Eyes On The Road (Pedestrian)

Eyes on the Road alerts you not to use their phone while walking.

Eyes on the Road (Pedestrian Edition) hopes to prevent pedestrian accidents due to overly-engrossed use of mobile phones while walking. It works by alerting you, via a notification, when it detects that you are walking and your device’s screen is on, unlock and facing up at the same time. There is very little or no interaction needed as the app detects these conditions in the background.

If you find the alerts are too frequent, you may tweak the walking detection sensitivity in the Settings menu.