HR Speed Transmitter

Your phone will be converted into Bluetooth server which will broadcast treadmill speed to any compatible application.
This way, your phone will act as a standard running speed and cadence sensor. 
You will be able to set manually your running speed with 0.1 increase step up to 18 km/h (11.2 mph).

The free version is limited to five minutes, otherwise you will have to purchase the full version of the application.