Thermostat Widget for Android L/M
Here is my version of the widget for Android with realistic controls unlike everything that has been posted earlier.
Swiping horizontally inside the widget will switch pages of the launcher, and dragging a knob by a circular path will cause misoperations, it's difficult to move a finger by a circle without any physical limits.
That said, I'd swipe vertically to set the temperature, tap arrows at the bottom to switch between rooms, tap gear icon to open the app and setup schedule or whatever.
In the center of the screen you can see set temperature.
Background color changes depending on the current temperature from red to blue in the range 40-90° F.
Once you set the temperature, you will see how soon it will be applied (in 5 min on the screen), and you will see small current temp (80° on the screen).