Hi,
Well it only uses a 1.5 volt battery for power so the only real safety issue is to the thermometer I think as long as it is fixed correctly.
If it gets P'd on or dunked in the water bowl it is probably a goner.
You could try fixing it to the side with velcro - or a hot glue gun holding the velcro on to make sure there is nothing the snake can get stuck too but you can remove the unit easily for cleaning.
You could use the glue gun to hold the thermometer but that might be annoying in the long run.
Main things to remember;
It's nice to be able to read at different points of the tank easily (hence the probe idea).
At some point the snake is likely to try and climb/sit/P on it.
No Tape inside the tank.
dr del