I have the Big Bike Parts handlebar mounted TPMS, love it. Kind of pricey, but the rear tire valve of the VV is a first class pain to get to so I think it's worth it. I have the tire pressure and temperature if I want it at a glance. It tracks with my handheld tire pressure guage very accurately. I like the handlebar mounting much better than the keychain unit.
Wish I could lock it on the bike, but fortunately it is easy to pop on and off. Wish it were rain proof, but they provide an ugly silicon cover you can put on in the rain.
Garmin now offers TPMS capability with some of their GPS units, so there would be one less thing attached to the handlebars.
2010 Vulcan Voyager /Ooops - I totaled it!/