Calling all runners!

I am in need of advice... exercise advice!

I know there are all kinds of gadgets & gizmos to track my workout information, heart rate, calories burned, speed, distance, etc. I am wondering if a person really needs one of these devices & if so what should I look for? Do you have one? Do you like it? If not, have you heard good things about one? I would really appreciate any tidbits you have to offer up on the subject!