The OEM Goldwing TPMS is what I would call a simplified system that is typical of those made specifically for motorcycles. The OEM system is illustrated below and consists of three parts... two sensors/transmitters in the tires and a controller that monitors the transmitted signal and produces a low pressure warning when appropriate.

TPMS sensors have three function blocks: 1) a sensor that measures pressure and temperature, 2) an RF transmitter that sends the measured data to the controller, and 3) an LF receiver that accepts commands and issues them to the RF transmitter. A "simplified" system is one that doesn't have a built-in way to issue commands to the LF receiver in the sensors.

Why would you want to issue commands to the sensor? Read on...

The second picture below is an exploded view of the Goldwing sensor; this is typical of any other sensor on the market. The three function blocks mentioned above are implemented with electronics on a tiny PCB housed in an enclosure with a battery. Function 1, the sensor, is a tiny analog IC that continuously reads pressure and temperature. Function 2, the RF transmitter, is a programmable microcontroller that reads the analog pressure and temperature data, converts it to digital, and transmits it to the controller on a 315 or 433 MHz carrier. And function 3, the LF receiver, is an LC tank circuit tuned to pick up 125 kHz signals and send them to the microcontroller.

The OEM sensor uses built-in accelerometers to send motion data to the microcontroller. When the bike is parked and the microcontroller does not sense motion for 7 minutes, it will not transmit data and therefore you cannot read tire pressure after the bike has been parked. This is done to save battery life of the sensor. When you get on and ride faster than 9 mph for 20 seconds, the microcontroller senses this and begins transmitting data every 1 minute. This is a cheap usability feature IMO because the most important time to check pressures is in the morning BEFORE you ride.

If the bike had an LF command module it could be configured to detect a key on, and when it sees the key is on it can send a single transmit command to the sensor... and then allow the sensor to go back into sleep mode until the accelerometers take over. With this setup you could read pressure whenever you wanted and not really affect sensor battery life.

So where can you get an LF command module that will do this? That's the complicated part... do-able but complicated.