I use the IPBike app (Android) on my phone combined with cateye cadence/speed sensors and a garmin heart rate monitor. I use a phone mount that takes the place of the riser cap. This totally replaces the Sigma Rox 9.0 that I used for years, and I couldn't be happier with the setup. It's essentially the functionality of a Garmin for a fraction of the price.

IPBike can be used standalone with GPS only, if your phone does not support the ANT+ protocol.