A week seems like a short amount of time. If you're dead, we're not talking about safety here—urgency is less important. I think even a mail every month would be sufficient.
That's what http://www.deadmansswitch.net/ (disclosure: I wrote it) does, it also has configurable intervals so you can make them as short or as long as you want. It sends you an email every interval, and, if you don't reply to any of them, it sends your messages.
