It looks like the Bluetooth heart rate monitor strap and software announcements and releases are heating up. Wahoo Fitness and SmartHF have both announced Bluetooth 4.0 Low Energy Profile heart rate monitor straps. The advantage of these HRMs is that they do not require the use of a dongle that plugs into the phone. This means that battery life can theoretically be made longer, and you can use your current phone skin or carrying case.
The Wahoo Fitness HRM is called BLUEHR. The HRM is a SmartHRM strap, and connects to your iPhone (currently works with the 4S only) using the new Bluetooth Smart technology, known as the Bluetooth 4.0 Low Energy Profile. The HRM is waterproof up to 5 feet, and is expected to start shipping in January 2012. The current HRMs that Wahoo makes are compatible with dozens of apps, so in the long run I would expect all of the app writers to jump on board. I have included a video from Wahoo Fitness below:
SmartHF is selling the SmartHRM Bluetooth model that works with Android phones. The product works with SportyPal, JogTracker and Jog Tracker Pro, SmartHRM fitness App, and Jogger. Data can be stored for up to seven days, and comes with an internal rechargeable lithium ion battery. Weight is 2.4g. The SmartHRM Bluetooth model retails for $99.00.
SmartHF also sells the SmartHRM WiFi model that works with the iPhone. The HRM strap works with CardioMapper, SportyPal and body-PRO. This unit allows direct connection via WiFi to the iPhone, so there is no additional hardware required. The strap has a built in rechargeable battery that will last approximately 6 hours. The strap is compatible with all iPhone models, including the 4S. The SmartHRM WiFi model for iPhone retails for $129.00.