Ofo and GridBike operate here in Mesa. The bikes are all over the place, but are most notably at bus stops (which isn't surprising, of course).
I haven't tried either one, though I do have the app on my iPad.
Other news: the Giant Revive is back in business, after suffering a flat tire in the front. I now also have a supercool basket on the back, instead of the saddlebag I was using to store stuff. I can actually use the bike for more than just back-and-forth stuff.
Now, I only need to convince the wife to let me use it out on the city streets...