You probably already know this, but if you get a post-paid T-Mobile USA SIM card, it'll work in most places with unlimited (limited-speed) data, which I've found is more or less good enough for calls, maps, etc. (You can pay extra for LTE-speed) It's $50/mo, but there isn't a contract. Calls are ten cents a minute or so. Coverage in the Alps is theoretically fine, but you'd want to double check against the partner carriers.

Looks like France, Italy, Switzerland, Germany, Netherlands, and Belgium are covered under the unlimited deal, Monaco is possible (but not unlimited) and Liechtenstein doesn't have a roaming agreement with T-Mobile.

Dunno if that meets your needs, but figured I'd mention it.