I've been thinking about grabbing some sort of heart rate monitor + step counter for tennis because I'm a nut for statistics and I want to get some hard quantitative data from my time playing/training. Ideally, this device would interface via bluetooth but USB is fine too. It would also be nice if it had some sort of android app that works with it. Polar seems to have a few possible solutions but I wanted to check here first to see if someone else already found the holy grail. Anyone have any info/experience? Thanks much!