You might need to be a bit careful, as Polar make several different transmitter units...
There is the T31/Wearlink coded units used with RS100, RS200, RS300...
Then I think there is a non-coded version for some cheaper "fitness" watches.
Plus the Polar Wearlink W.I.N.D. used with the RS800 and other high end models
Then they make a Bluetooth version so you can use it with a Nokia, iPhone or Android mobile phone and use the phone GPS - see
http://www.sports-tracker.com/
I'm not 100% sure, but the one you have for Nike+ could be different again, although from the second link below it looks like it might work with some polar watches...
I tried adding the links and got this message:
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if this is error