Shameless plug for Jeff and SmarTire (and actually against my own interest).
I've been running the SmarTire system on my FJRs for the past 13 years, and I agree with Jeff. IMHO, this is by far the most sophisticated TMPS ever for this application. With the sensors mounted internally, it has no security issues, retains the tire valve's redundancy for air retention, and more importantly, senses the actual air temperature within the tire. The temperature-compensated pressure reading on the road is a no brainer (no math, no fuss), and the constant monitoring enhances safety and peace of mind. The electronics are very reliable, and the sensors are long lived.
The only failure of the TPMS system I ever experienced was due to the sensor band clamp eventually failing after being over torque'd by the dealer's installer. And that failure still left all the air in my tires.
Bendix bought out SmarTire ten years back, and promptly pulled this product from the motorcycle market (f***king Bendix). Perhaps that made good business sense from a liability or other stand points, but from a safety of life perspective it was a huge disservice.
So don't be put off by SmarTire's lack of support. Get 'em while the last few kits are still available!
YMMV.