I have a Resqme tool clipped to the sun visor of my car. The window breaker is spring loaded so it’s much smaller and lighter than the hammer style tools.
I’ve never needed to use the tool or had an opportunity to test it, but my brother has tested it and said it worked well. He’s a firefighter and has also had a fair bit of rural road rescue experience so I trust his opinion on seatbelt cutters and glass breakers.