I don't believe drilling a small hole in the back bottom corner of the safe would affect the fire ratings. You could put a contact and tilt type sensor inside. Most smaller safes have designated places to drill for bolts on the bottom that are sorta raised feet - you could do another hole nearby where there's clearance on the bottom just small enough for an 22/4 security wire. The safe is otherwise sealed - it's not going to be drawing fire in - and the point of the concrete/firerock inside all around is to spread the temperature out and keep it from getting too hot - one pinhole won't change those characteristics.
Part of my reasoning - I have a large executive safe. I had to have warranty service on it, so while the tech was out, I had them upgrade to the latest and greatest power passthrough that now also includes passthrough for USB, RJ45 and even a security sensor. They did have to cut a little more of the firerock (basically fire rated sheetrock) out but promised this is how all the new models leave the factory and it has no impact on the fire rating. The firerock and steel still handle the heat dissipation; worst case is the outlet can melt but it's mostly metal.