iOS (Jailbroken): One of the problems with iMessage is that the service doesn’t automatically group your contact’s different information together. So, if you get a message from an email address, it doesn’t combine that with previous messages from a phone number. Merge is a jailbreak tweak that fixes this.
Merge seems simple, but it works really well. Instead of creating message threads based on the contact number, it groups the threads together based on the contact name. So, if you receive a message from someone using iMessage on their computer from an email address, it’ll be linked into another message sent from their phone number. You can find Merge in the ModMyi Repository on Cydia.