Cool app.
From a design perspective it might be a good idea to get a favicon and change the title of the website to something a little less generic.
I know this is fairly new, but it would be cool to include some sort of contact info, maybe get facebook/gmail integration.
Also maybe add an option for a time (ie between 6-8pm), I know you wanna keep it random (in terms of which day of the week or month) but if I set it for someone in Europe, and it reminds me at a time when Europe is probably asleep it's not very helpful.
Other than that I like the bare-bones feel, it's clean and hopefully works!
Just a couple quibbles, overall cool implementation of idea.
