Rematch is a pet journal alternative for managing pets and teams.

Features

Save loaded pets into teams for use in future battles
Save these teams to targets and easily recall them when you battle the targets again
Organize teams with drag and drop into a scrollable list of groups
Choose pets to level and automatically slot them with the Leveling Queue
Find counters with extended pet filters such as Strong Vs and Tough Vs
Search for abilities and text within abilities
Add notes to teams or pets as reminders or to find later with search
Share teams with other Rematch users with export/import or directly sending to an online player
Use integrated with the pet journal or in a minimizable standalone window
And much, much more!

How to use

Rematch initially replaces your regular pet journal. You can switch back to the regular journal anytime by unchecking the Rematch checkbox at the bottom of the journal.

Alternately, a movable and minimizable standalone window can be summoned a few ways:

From a key you define in the game's key binding interface
/rematch macro command
"Use Minimap Button" in options to create a minimap button
From its LDB button if you have a Broker infobar addon

Aside from the familiar list of pets and your loaded pets, Rematch adds another panel that switches between these tabs:

Teams: Your saved teams and the groups they're stored in
Targets: Notable targets with known pets grouped by their expansion and zone
Queue: The leveling queue of all pets you want to level
Options: Settings to change many aspects of Rematch

Tooltips explain many parts of the addon. Poke around and experiment! Check out the many options. There are several views and a lot of features to the addon you can discover over time.

Standalone Window

From the start, Rematch was built to work independently in its own window detached from the journal. As a standalone window, Rematch has several benefits:

It won't cover or disrupt other addons that modify the journal.
It can display information more compactly in single or double panels in addition to the three-panel view like the journal. Click the left and right buttons in topleft beside the lock button to change views.
It can be minimized so you can view and interact with loaded pets without covering a large part of the screen. Click the minimize button in the topright of the window beside the close button.
When interacting with targets, the more compact views don't obscure the view of your targets or surroundings.
You can keep it on screen while doing a round of battle pets or during a battle; then dismiss it when done.
Many options in Rematch are designed to summon the standalone window, some automatically (Safari Hat Reminder, Interact Options), some manually (Minimap Button)

Loaded Team

Above the loaded pets is a button with a gold background that will display the name of your loaded team, if one is loaded. When no team is loaded it will say "Battle Pet Slots".

Clicking this button will reload your currently-loaded team. This can be useful if you have a random pet in a slot and you want to pick another random pet.
Right-clicking this button will display a menu as if you right-clicked the team in the Teams list.

Teams

You can save an unlimited number of teams in an unlimited number of groups.

When saving a team, if you choose any targets in the Targets tab, Rematch will know what team to load when you interact with those targets later
Teams that contain targets have a red target icon to the right of their name
In the Options tab you can go to Interact Options to choose what you'd like Rematch to do when you interact with targets that have a saved team
You can show up to 16 tabs as "bookmarks" to team groups that will display on the side of the Rematch window
You can add notes to teams either from its right-click menu or by clicking the notes button to the right of the loaded team button (described below)
If you'd like Rematch to build a team for your current target, click the little blue dice icon and a random team will be loaded. If the pets for the opponent's team are known, it will build a counter team that's strong vs and tough vs the opponent's pets. If you like the team don't forget to save it!

Pets

To help make these teams, Rematch has expanded filter options, a Type Bar (opened by clicking the arrow next to the search box) for easily finding counters, and enhanced search ability.

If you open the Type Bar there are three tabs: Types, Strong Vs and Tough Vs:

Types allows you to quickly filter to a specific type or group of types.
Strong Vs will filter the list to pets that do increased damage to the chosen types. For instance choosing Magic will list all pets with attacks that are strong against Magic (all pets with Dragonkin attacks).
Tough Vs will filter the list to pets that receive reduced damage to the chosen types. For instance choosing Magic will list all Mechanical pets.
You can combine these to find double counters: For instance Chi-Chi, Hatchling of Chi-Ji is a flying pet with all elemental attacks. If you select Strong Vs Flying and Tough Vs Elemental you'll get a list of snails and other critters with magic attacks.

In the topleft of the Type Bar is a level 25 button. Click this to quickly filter for level 25 pets. Right-click this button if you'd like to list only rare-quality level 25 pets.

In the search box, you can not only search for the names of pets and their source, you can also search for:

Abilities ("Call Lightning" will list all pets that have this ability.)
Text within abilities ("Bleed" will list all pets that cause a target to Bleed or is affected by Bleeding.)
Level ranges ("level=25" or "level>10" or "level=8-13" will display specific levels or a range of levels.)
Stat ranges ("health>700" or "speed=250-350" or "power>276" are some examples.)

Also:

Information about pets are found in a pet card that acts like a tooltip.
Clicking a pet while viewing its card will lock the card in place so you can mouseover parts of the card for more details.
While viewing a pet card, hold <Alt> to flip the card to its back for its lore and where the pet can be found. You can also mouseover the icons at the top of the card to flip it over.
Like teams, pets can have notes attached to them from their right-click menu. You can use these notes for anything you want to remember about them, or for tagging purposes: add "#find" in notes for pets you want to find, and then search for "#find" to list all pets with this tag.
Pets can also be marked with Pet Markers (star, diamond, moon, etc.). These can be renamed for any purpose by clicking the gear icon beside their name in the Filter menu.

Queue

Rematch has a robust system for leveling pets with the leveling queue. The queue is a place to put all the pets you want to level.

You can order the queue however you like, or let the addon sort the queue for you.
To mark a slot for leveling pets, right-click one of the three loaded slots and choose "Put Leveling Pet Here". When a team is saved with these designated leveling slots, the slots will be filled by the top-most pets from the queue (or the most preferred, see below).
You can also right-click a pet in the team list and choose "Put Leveling Pet Here" to convert a slot in an already-saved team into a leveing pet.
When a pet reaches level 25 (gratz!) it will automatically leave the queue and the next leveling pet will take its place.
In the Queue button menu, you can fill the queue with many pets at once. For instance: in the pet panel, filter pets to High Level (15-24) and Rare, then choose Fill Queue to add level 15-24 rares to the queue.
For some opponents, just grabbing the top pet from the queue can kill your low level pets, or you want finer control over what pets load for a specific target. If you right-click a team that contains a leveling pet, you can click "Set Preferences" to choose various health and level ranges to refine which pet the queue will pick when a team loads.

Sharing Teams

Teams can be shared with friends directly in-game or through an export/import feature.

To share a team in-game with another Rematch user, right-click a team and choose Share->Send Team. A dialog will ask for a name, which can be either an online character or a battle.net friend. If it reports the team was succesfully sent, the recipient now has a popup with your team they can save.

You can also share teams by exporting them from the same Share menu. If you paste this exported text or string elsewhere, someone else can import your team by copy and pasting it into the Import Teams dialog.

You can share with yourself too! If you don't regularly backup your SavedVariables and want an easy way to backup your teams, go to the Teams button at the top of the teams panel and choose Backup Teams. It will export the whole tab in string format. Paste this text in an email to yourself or in a text file someplace to keep a backup of your teams.

In Conclusion

There's a great deal more to Rematch. Play around with it and experiment. See if you can create new team combos that have never been tried before. Thanks for using it!

If you have any suggestions, feedback, bugs to report or anything else you'd like to share, feel free to leave a comment here.