I bought TireHawk's Gen II TB-X04C system, and the good news is that you can see your tire pressures on the Sion unit
It has a little box which receives the sensor info from the tires and creates a wireless network Sion connects to, so the android app can display the sensor info.
The not so good news (minor glitches):
1. as you can see, it displays in landscape mode (the app also has a portrait mode, which seems to be the intended primary usual mode). From landscape mode, there is no access to the settings menu (or SmartLog, or About menus)
2. when the tirehawk app is in the foreground, it turns my music off! I'd like to be able to see the tire pressures and play music at the same time. (Apparently this would work if there was access to the settings menu)
3. calibration: the 4 sensors produce slightly different readings. sensor (1) and (4) read the same, sensor (2) underreports 1 psi, and sensor (3) underreports 0.5 psi.
It would be pleasing if the screen showed identical readings, when the pressure was identical.
4. Read out is in 0.5 psi increments eg 37.0, 37.5, 38.0; it would be helpful to get 0.1 psi increments, so I can calibrate them exactly, and after that's been done, to round up screen display to nearest whole number.
5. the external sensor is a little bulky: