Closest I've been to no maintenance has been Magura (two sets of Louise and one set of Marta) and Shimano, however I did not like the Shimano feel. Currently have Hope Tech V2's and they work well, but they did need attention to keep the pistons coming out evenly in the beginning.
I also had Tech M4's for a while. I just could not get the pistons to come out evenly what ever I did, and finally got rid of them. A friend had two sets (four calipers) of M4's and had the same problem on one of the four. He studied the issue quite a lot, and noticed that whatever caliper he put the pistons from the problematic one on, had the same issues. Also changing seals did not help... He figured it would be a tolerance issue, that is the pistons would not be exactly the same size (or something like that) resulting in them working a bit unevenly. Sounds pretty logical to me, but was never suggested from Hope when I was trying to find a solution for the problem (never got one).
However the feel of the brake on the V2 is the nicest I had on anything, with the Maguras as a second.
edit: I did also have BB7's with nice cables and levers back in the day. They where very fit and forget, all that was needed was manually adjusting the pads now and then, and it was very simple and fast. They did not have the feel of good hydraulics, but if reliability was the main factor then you can't really go wrong with them. I did notice the lever and cables seemed to make a big difference on how they feel, so keep that in mind if you get a pair.