I had a fiddle with some Estimotes for a research project last year. Managed to get some fairly inaccurate indoor location tracking going on Android using 4 beacons and some fudged trilateration functions, then did some cool location-based things with Philips Hue bulbs. Was a blast!
Keep up the good work, can't wait for the Android Indoor SDK! (I appreciate that it's more effort due to differences in device hardware, etc)