http://www.amazon.com/gp/product/pro...1868259&sr=1-2

I don't see why it would be an issue:

1) If the bike is really different as in size of wheels and grams it may mess up some data;
2) You can buy the hrt strap or the cadence apart...the 305 would have to register the other ones first...there may be a bug in there but is seems more than ok to do