Beeper Mini is really good. My Android bestie is finally a blue bubble. Thank God. https://play.google.com/store/apps/details?id=com.beeper.ima&pli=1
Beeper Mini: Chat With iPhones - Apps on Google Play

Finally, get blue bubbles on Android!

@film_girl How trustworthy is that app? How did they accomplish this? I have… reservations.
@chartier @film_girl jailbroken devices and/or vms iirc
How Beeper Mini Works

It's a technical deep dive, so buckle up!

Beeper Blog
@film_girl @chartier oh my b! I remember original implementations requiring this, that's neat that they RE'd the protocol
@b3ll @film_girl @chartier I had just assumed access to iMessage server endpoints would be dependent on something signed by something derived from the trust root in the phone. You’re saying it “just” required reverse engineering the protocol?!
@ratkins amongst other things, looks to be based off older implementations of iMessage (in a similar vein to how Hackintoshes did it)
@b3ll I wonder how old the oldest phone is that is still capable of sending iMessages…