Sparrow
Sparrow was already working for Android users, so an acquisition makes sense.
Sparrow announced to its users Friday that it was acquired by Google and would transition to Google's terms and policies by Aug. 24.
Now we're joining the Gmail team to accomplish a bigger vision — one that we think we can better achieve with Google. . . . We’d like to extend a special thanks to all of our users who have supported us, advised us, given us priceless feedback and allowed us to build a better mail application. While we’ll be working on new things at Google, we will continue to make Sparrow available and provide support for our users.