For a project I just started, the Wixel MCU from Pololu seems to be sufficient for what I need (namely: 1 UART for Dynamixel servos, and a wireless serial connection).
I figured I'd use my Arbotix Commander for the controller. Since the Wixel's use some custom hardware wireless communication method, I need two of them (and I bought two of them for $20 total on Black Friday); one on the bot, and one to forwards the commands from the Arbotix.
I used some of the spare connections on the Seeeduino that is part of the Arbotix Commander V2, wired these to some female headers on a chunk of perf board, and stuck stuff together with double sided foam tape.
I first verified that the Wixel forwards the Arbotix Commander signals with the USB-to-Serial App that Pololu provides. And I've now succeeded with using the Wireless Serial App on both Wixels so that Arbotix Commander signals are sent to a PuTTY terminal on my computer. Not to be a shill, but that was easier to set up than any MCU + Xbee configuration I've seen.
And pictures: (Click to embiggen)