We have always had to reboot into recovery to make a nandroid backup. If you are like me it can be a pain to have to reboot into recovery and sit there for several minutes waiting for a nandroid backup to complete. Most of the time i end up just going willy nilly with no protection. Really you probably think I am just lazy but think about it how many times have you rebooted into recovery to make a nandroid to find out that you have missed a call or text message. Maybe not many times, but one time is to many. Developer "ameer1234567890" has created a solution that allows you to create nandroid backups while online "that is while your phone is powered up and running android". It does require a few things. Your phone must be rooted, you must have a terminal emulater installed, you must have busybox, and a working clockworkmod recovery installed. Once you have everything set up backing up is as simple as opening terminal emulator, typing su, then typing onandroid. Then just go back to doing whatever it is you were doing while it does its thing in the background. Pretty groundbreaking stuff if you aske me.
More info and downloads via XDA