Use your phone running indoor on a treadmill and enjoy sport simulation apps such as Zwift or Arcade Running on a second device. Treadmill Speed Transmitter act as a bluetooth low energy foot pod and sends running speed and cadence to your tablet or computer.
There are different modes : you can either set the speed manually or put your phone in an arm band (or take it in your hand). In this case, running speed will be computed automatically. In addition, you will be able to adjust running speed by setting up step length parameter. In order to get better results, we advise you to do this when you are running around 10km/h.
Other options :
Use your ANT+ Footpod with Zwift. Your phone act as an ANT+ -> BLE bridge.
Use your Garmin watch with its integrated accelerometer with Zwift.
The app is free for 8 minutes workouts, if you want to do longer exercices, you will have to buy the full version.