Electric Tart Burner Warmer with a Timer - Safer Alternative for Home Scenting
Update 7/20/2013: Looks like the above item has been discontinued, but I found another one on Amazon. It's just the hot plate base, but you can buy a ramekin or glass votive holder to warm your tarts on it.
Update 11/3/2014: I found this wall plug in 24 hour timer, just plug your tart warmer into it and set the timer to shut off when you want. Easy!
Full disclosure, if you click on the links and buy from Amazon, I get a tiny commission. Thank you!