I bought the FOBO Bike TPMS $100.00 4 months ago.
It seems to be very good / works with Bluetooth to your cell phone (Android or I-Phone)

The bottom line is I like the system!


Positives:
Inexpensive
I always ride with my cell phone
If I switched bikes I can move it easily
It seems accurate compared to my HD pressure gauge (Harley has to be right)
If I remember to start the app after I turn my phone off it will warn me if pressure is low as I walk up to bike or sit watching TV in the living room.
This waring as I walk up to the bike will give me a chance to put air in before riding when the readings are valid and accurate.
It will give a catastrophic (very low warning) warning if you can hear it.
When traveling I always have my cell phone's GPS on even if listening to the bike radio. (so I should it should cut in and give me a warning)

Negatives:
I have to remember to start the app after my phone has been turned off (Maybe I can get an app to start the app)
It warns me when I am watching TV (ha ha)
It is only accurate when the tires are cold (no compensation for heat) so the warning will not help for slightly low tires on the road.
You can get a good feel for where the pressure should be if you watch it for a while.

Steve