As most readers will realise, making an alarm clock with an Arduino isn't really anything new (however everyone should do this at least once). However the following example by Erik Nilsson is much more interesting. Not only is his device a normal alarm clock with a reasonable user-interface, it can control mains power outlets via 433 MHz RF wireless control. So when it comes time to wake up, the clock can control a lamp, stereo, turn on the towel warmer in the bathroom and more. A great example of how you can safely do home automation without any mains wiring with Arduino:
If you're looking to work with your own RF wireless hardware, but don't want to make your own receiver circuit - check out our range of 315/433 MHz receiver shields:
Apart from being idea for working with the various low-cost data links on the market, the shield can also be used to capture wireless weather station data, as described in the book "Practical Arduino". For more information and ideas, check out the product page.