Light aircraft engines are already _very_ reliable, you'll most likely spend a career flying without ever experiencing a failure. The most popular GA motor, the Lycoming O-360, has been in production for something like 60 years, and is pretty much "debugged" as far as engines go. Still, failures do happen (most often because of user error). You can switch to turboprops, and you'll get more reliability, but higher costs. You can switch to a multi-engine plane, but again costs are higher.

An electrical motor which can provide backup assistance without causing further single points of failure is a nice add-on if they can make it work (I'd be sceptical about trusting this thing without extensive testing.)