Try Kustom Widget (KWGT). It's a scripted mini app maker that exposes a lot of the phone internals, and it keeps expanding. The developer is really responsive to feature requests. I use it with my home weather station and a pi-based sensor network to monitor home security. When I get my solar installed, I'll add in the status of that system. The major limitation is that KWGT is event driven, with a minimum update interval of once a second. This interval has a major impact on battery life, so the default is one minute.