Pushbullet is ok, but with OSX its only a browser add on. With the way that OSX switches windows, its kind of annoying when I'm working and need to send out a quick message. And yes, I know I'm being picky :)

I also tried MightyText, but they kept adding useless junk to the already bulky interface. The service itself also wasn't consistent.

Overall, I'm surprised that Google hasn't flat-out copied iMessage.