Xantrax offers one integral into their Trave SW series as well as they offer a standalone unit for a couple of hundred bucks. I've installed and used both and I don't think that one is better than the other. Very handy to have, especially if you set all of the limits and Quiet time functions properly.

I don't think they are that hard to install, as long as you sit down and read the manual a couple of times. Especially easier to intall if you have a fancier generator that uses a start/stop button, electronic shutdown system, as apposed to a key with a mechanical Murphy shutdown switch.

When using the installing them , I recommend using some relays in between the generator and the inverter so that the inverters relays are only powering the additional relays, instead of a generators starter solenoid etc. If something overloads or shorts it's better to replace a $5 relay than a $2500 inverter.