Had a rear flat the other day on my CB750 - scary. That was my first flat since I began riding in the mid 60's. My wife is new to riding an has a VT750 which also has tube tires and I'm nervous about her getting a flat so I've been looking at tire monitors as an early warning. Are there any that have senders that can be recharged or take a battery change? Near as I can tell you have to buy new senders every 3 years or so. Also, any recommendations on brand would be appreciated.