In the past I was using Stryd, bur with the native power support of the FR955 I switched, but this was not a good idea. The Workout Screen is not adjustable and the power lags so much, that short intervals are not really possible. Although the messages (are so slow and are so long shown, that you cannot see if the interval is over. The power values that are shown are jumping around without changing the pace or up/down. Its really that bad, so that I will switch again to Stryd. I am using a Tri-HF-belt.