Are there any heart rate monitor apps compatible with any chest straps?

think mostly the straps only support the makers software and the other way around

http://www.withings.com/en/bloodpressuremonitor

http://mashable.com/2011/07/03/review-two-blood-pressure-monitors-for-iphone-ipa d-video/

http://www.ihealth99.com/

If you have an iPhone 4S (or any iOS device with Bluetooth 4.0) there are at least two chest strap heart rate monitors available. There are dozens of apps that support these HRMs.

Wahoo Fitness Blue HR

http://store.apple.com/us/product/H8296VC/A

Polar H7

http://www.polarusa.com/us-en/products/accessories/H7_heart_rate_sensor

I have been using the Wahoo Fitness Blue HR for the past month and it has been very reliable and durable.