No point in wasting so much money to secure a rescue tool to a seatbelt, and probbaly a very bad idea in terms of real safety. Just get one of the very simple cutters and window breakers designed for such usage. To free yourself it is not the right tool. To have it for other emergencies, secure it in the vehicle in another location, if one has a driver's side door pocket, that would maybe be ideal.
I really like what Vic did with the recue tool, of course like many SAKs, not the one for me but I still love it.