Funny I had been planning to build something like this. My idea was that you would forward an email to the service and just type in the start of it when you want the reminder. Using some simple NLP you'd be able to write something like "next week" or "on Monday" and the system would then email you back when it wanted to remind you.

No need to have your gmail password, or even be gmail specific.

Is there anyone out there who would use this? Enough yeses and I'll build it.