Mike,
Maybe I didn't tell the whole truth with regard to Bluetooth. What you propose may work, what would happen is each BT module, on the 'floor' could buffer and then talk to the main PC in turn so the data will get there but not in real-time if another unit is already connected and using the link. This is dependent on the units allowing un-paired operation so you don't need to go through a pairing sequence each time a new unit (identified by MAC address) connects to it.
The new low power Bluetooth specification, or Bluetooth low energy as my old company calls is (
http://www.csr.com/home.php), allows much of this to happen while dropping the link to save power. There are very few devices available just now which support low power Bluetooth at a hobby level. Low power Bluetooth is designed for sensor networks with a single battery giving years of power and then possibly the unit is disposed of when flat such as pedometers in shoes, pulse-rate monitors in watches etc all updating your mobile phone in a 'push' method with minimal signalling and thus power consumption.
Even though you say your idea is already out there, there is no reason not to make it a product, PICAXE is cheap and with the right features you can make it fit the need. I would also consider ways of linking the weight lifting, cycling distance or whatever into the PICAXE too using one of the inputs, you only need to send the total counts to the PC and do the number crunching there, you could hardcode each PICAXE with a station ID which is mapped on the PC as you might only see 20 reps for weight lifting but thousands [of revolutions] for cycling. Just an idea.
