I am so grateful to Sparkfun and Google for creating the IOIO board. Smartphones make such a useful programming platform that I'd been thinking about how to create something similar. But it would have taken me years to produce a board even vaguely useable!
I got the demo program working on a Motorola Droid Milestone. This is not the Droid X, which is listed as a tested platform on the Sparkfun site, but an earlier model of Motorola smartphone. I powered the board from a powered USB port. By a powered USB port I mean a USB port in a desktop PC. Your laptop may only be able to supply 100mA from a USB port when running from battery, whereas a powered USB port can supply up to 500mA. The issue is that the phone will try to recharge itself from the whatever is powering the IOIO board, unless you can disable this automatic recharging. A few tests using a lab power supply unit shows that the board only pulls about 60mA when the phone is fully charged. But once the phone gets a little thirsty, the current requirement goes up to over 200mA, so that the battery on the phone can recharge. At full throttle (potentiometer turned all the way) the current draw goes over 400mA.
Figure 1 shows the Milestone happily connected and talking with the IOIO. Figure 2 shows the mini USB connector that I soldered onto the back of the IOIO. It fits on neatly. You may have to twiddle the potentiometer on the top of the IOIO until enough current is supplied to the Milestone for the board to be recognised. If you choose to solder on a mini USB connector - check and recheck that your socket pins go to the correct tabs. It would follow Murphy's law that your socket has different pin spacings than mine!
Figure 1: Motorola Droid connected to IOIO, running demo program