Hackers Keyboard has that via ctrl+z, but only in horizontal mode. For this only i had my Galaxy S3 in horizontal per default. But can't do that with modern phones' aspect ratio and i'm missing undo since then.
Man why couldn't there be a keyboard like this that also has swipe typing D: I miss the ctrl-like functions of the Swype logo button on the Swype keyboard so much, specifically the select all and the select-one-word abilities