I know it isn't exactly what you were asking for, but I have a Time Capsule. The problem with any external drive is that it still has to be connected up for the backups to occur... this is totally set and forget. The only issue is I'm hearing there's overheating issues with the power supply in the TC (guess if it breaks, I'll get it replaced and start a new backup, but if you want to go back in time, its not necessarily the best option).
Or maybe if you have an external drive, hook it up to an Airport Extreme. Just be sure to do the first backup wired.
Or maybe if you have an external drive, hook it up to an Airport Extreme. Just be sure to do the first backup wired.