If your doorbell is too loud, inaudible, or just plain dull, the Swann Wireless DJ Doorbell lets you customise it with any MP3 file. Even better, it rings wirelessly so you can put the receiver in any location you want (up to 100 metres away).
The $69.95 device works with a doorbell that you can attach to any doorframe, and includes a receiver that's actually an MP3 player. The receiver comes with 32 built-in tones, but you can add your own by placing MP3 files on an SD card.
You really only need a single tone to customise, but if you want a little variety you've got the option. Both the doorbell and the receive run off AA batteries. If you've got a problematic doorbell or just want one you can customise, check it out.