Concept 2 Rowers are quite popular among athletes. They are more than give you a killer workout. Thanks to the Concept 2 Rower iPhone Cradle, you can use your smartphone to keep an eye on your stats while rowing. This accessory is compatible with PM5, PM4, and PM3 monitors.
The cradle slides onto the top of the monitor and accommodates smartphones from 2.25 inches to 3.5 inches. Costs $5 at this time.[where to get it]