Wahoo Fitness is coming out with a Bluetooth-based Heart Rate Monitor (HRM) strap that will work over the Bluetooth 4.0 protocol which allows for very low power consumption on the strap side, and a direct connection to the iPhone 4S without a dongle. Cost is going to be about $80. The new protocol and its lower power consumption should allow a lot more fitness devices to use the bluetooth standard, while maintaining their small size. Wahoo Fitness has a set of products for connecting your fitness regimen to your iPhone - what else is in the wings waiting after the HRM strap? Wireless Speed and Cadence Sensor for cycling and a stride sensor for running maybe?
I like my Fisica ANT+ key dongle that allows me to connect my iPhone to a Garmin-standard HRM strap, but this direct connecting technology looks great.
MapMyRide just released a new version of their App which is compatible with the coming Wahoo Fitness Blue HR strap; so things look like they are falling into place.