Timecapsule.io (http://timecapsule.io/ http://timecapsule.io/) works exactly like this. It was built for the exact same reason, although I think the purpose and

Timecapsule.io (http://timecapsule.io/ http://timecapsule.io/) works exactly like this. It was built for the exact same reason, although I think the purpose and problem was maybe worded a little more clearly here. *disclaimer - I built timecapsule.io