ok been using the ibike dash since January this year and I have learnt a lot about my fitness and my training, road faster TTs and even beat my PB on a 25mile TT using the ibike dash.
getting more consistent power readings have been plageing me for a mouths but finally I have solved my problem this is what I have found, first I live in the UK and the road here are not always good very bumpy and uneven, this curses the phone booth to bounce or flex up and down which in turn makes the iPhone’s tilt sensor not read it’s like it goes into brown out or shut down! In turn makes your power reading drop off!!!! The harder you pedal the lower it gets because it bounces more. On inspection once I figured out what was going on is that the phone booth flexes on its mount there is no slop on the mount just flex.
my solution has been too support the front of the phone booth on my stem to take out this bounce, I have used an old Garmin mount with a layer of thin foam and a rubber band to hold it down, it can still flex if you hit a big pot hole I didn't want it to ridged and brake, the result has been that on the same stretch of road that is bumpy and previously the power readings would drop off now they stay at the level I would expect to see

Take a look at the photos to see what I have done.
Mark