Generic battery question/ memory saver ?

Our daughter was home this weekend and Sunday afternoon her battery went dead in her 2009 Subaru. I jumped her with the Tacoma and we went over to the O Reileys to have them check the battery. His tester said what I figured and the battery was dead. First off I was amazed at what a battery cost these days but I had done a quick check before we left the house and the O Riley price wasn't out of line but still damn high.
BUT, the kid there is pretty sharp and he offered to put the battery in and since I have a cold I let him. He pulled out what he called a memory saver and had my daughter plug it into the lighter socket. He said that it had a small charge and would keep the memory in the computer and was a pretty slick little tool. Also it kept her radio pre sets which made her happy..
I have never heard of one of these. Is this something I should use when unhooking the battery on the Tacoma????

 

Yes. They have been around for quite a while.

 

x2 but be sure you plug it into a powered up socket; otherwise it will not work properly.

 

The only thing they are good for is to keep your radio presets. The second thing is they will keep the check engine light codes live if you are in the need of service and the mechanic needs to retrieve the codes.

They are neat tools if you have a need, but not really something that everybody needs.