A:AnswerDepending on your body shape it may or may not work while swimming. Most swimmer body types no, it has a tendency to slip off after a flip turn.
A:AnswerThere is a very good chance that the H7 will indeed work with your older Polar unit. I would contact Polar directly if you're concerned. We can be reached at 800-227-1314 - Mike @ Polar USA
A:AnswerNo, the H7 is not compatible with the Nike+ sports watch. Best Buy does sell a version of our transmitters however that does work with the Nike+ product along with exercise equipment at your local health club. Note that this version does not communicate on Bluetooth. Below is a link to Best Buy's website that details this product further - Mike @ Polar USA
http://www.bestbuy.com/site/polar-wearlink-nike-heart-rate-transmitter/1171698.p?id=1218265851868&skuId=1171698