Wahoo TickrX Running Dynamics
Though Strava pairs will with the Wahoo heart rate monitors, Strava doesn't make full use of them. The TickrX has quite of bit of extra data, like cadence, ground contact time, and vertical oscillation. According to Wahoo they have a public API so that third party apps like Strava can read the running dynamics from the sensor/heart rate monitor. This additional information is quite important when tracking our progress over time, and tracking our progress over time is precisely what makes Strava so good, so this would be an excellent feature to add in an effort to improve Strava.