I have a Pfaff overlocker which has automatic tensions. I rarely alter the tension controls at all. It's not electronic but it does have a manual control that lets you select the stitch you want to use. I think a lot of the new overlockers may have automatic tensions. I know the Elna does too because it's similar to the Pfaff.
I have a Pfaff Coverlock which is a combined overlocker/coverstitch machine. As one of the previous members said the Pfaff has auto tensions and I rarely alter them. The one I have - 4862 - has a dial to select the stitch you want, ie rolled hem, 3 thread, 4 thread, 2 thread, and it goes on and on. Once you select the stitch (or procedure) you just check against the diagrams to make sure your machine is set up as it needs to be for that stitch and then sew. I've found it excellent. The Elna is similar.
I like Bernina overlockers but I'm not sure about auto tensions on them.