Yes the m8 motogadget sensor works, its the same principle as the oem sensor.
Also the sensor from Daytona works damn well if you put a (comes in the package) magnet in one of the holes from a disc brake.
Source: me. Ive tried both and went back to the oem. Why? Finish and all work equally well.
The thing is mostly cauges/indicators that need some tinkering as almost all (digital) aftermarket speedometers can be set to work with either tire size (like the acewell) or set based on a continuous speed.
The more annoying ones are the rpm -fixable with noise reduction - and i do believe there are several options for gear indicators like the Axel Joost products. Personally i dont mind having an off - on light, I either know its in neutral or an even number gear. But then when learning to ride, i did so on a bike with no gear indicator and was told: "look young man, its all about becoming one with your bike, it will let you know when it disagrees with you" - old bald man with a firemans mustache.
And maybe somewhere the list comes in handy, but forum discussions are fun too. Leave some for our and the imagination of the younglings. :D