To respond to MrKurt's question about whether the keys are still neccessary if she has a pager, I would say yes. The thing that would worry me would be: What happens if the place catches fire? In the event of a fire (or earthquake), she needs to be able to get out NOW, not when you can get home to free her. Or, what if (God forbid) you die while she's locked up? (This was the theme of an extremely disappointing novel by Stephen King.)

By the way, how has this worked out for you? Could we please have an update?