Well that's true, but if they come loose or come off, the valve just closes and the reader bounces off into the hedge bottom. If the sender comes loose a little bit, the gradual loss of pressure triggers the alarm. So not sure where a concern would come from really. I really liked mine. They're especially handy for helping to set tyre pressures when loaded up like my 80 is. You can watch the temperatures and pressures together. Too much flex generates heat and faster pressure rise. Now I am not trying to be too scientific here but on a good run you can play with the pressures to the point that once running, you see little rise in temp and pressure from cold. For mine it was very clear that the rears were carrying more load than the fronts. Adding more air did seem to 'stabilise' the rears if that the right phrase. They didn't heat up as much once stiffened.
I've not had one leak I have to say. There is an o ring in there and once tightened and locked off, they don't seem to come loose either. Not saying they couldn't. But the only fault I had was one kept telling me I had a puncture. When I clearly hadn't. Nothing seemed to fix it and then when I went to get a new sender, they'd stopped that model