I use a power meter without a dedicated cycling computer like Garmin or Wahoo, I prefer to ride with my phone on the handlebars.
I found a couple of cycle computer apps which can be paired with the power sensor, displaying some power data during the ride: Ride With GPS, Wahoo Fitness. However, they only display the momentary power data, which is very "jumpy" from second to second (plus some other stats like max 20s power, or average/normalized power over the whole ride).
Is there an app that allows the user to configure a rolling window of 5/10/20/30 seconds over which to average the power data? It would be much more useful for pacing oneself or training with power zones.
EDIT: I've accepted the answer about IpBike, because based on the description of its features it fits the bill. However I'd be grateful for more answers specifically for iPhone apps, not only Android.