These guys have been around for a number of years and have an international presence.
The main part of the hitch is entirely behind the bumper cover...you need a fairly small hole underneath to access the locking pin (keyed) and the release (spring loaded), and the shaft slides up into the main part of the hitch through that hole. So, when not being used, the cutout is entirely underneath, not through the vertical, painted, bumper cover.
If you're interested in utilizing the built-in trailering functions in vehicles that have them (like my GT), there are only two smart wiring harnesses available: the OEM one made by Westphalia, and the aftermarket one made by RightConnections. The later is the only one that will work without having to program anything...this includes, as I mentioned, enabling the trailer stability control logic, turns off the rear PDC sensors (if present), and enables a special trailer rear view camera view. I don't think there is one for the i3.
FWIW, even though I've not towed anything (yet) with my GT, I did want the wiring harness functionality. Like what is required in Europe when a bike or something similar can obstruct the rear lights, I run a light bar on the harness that duplicates the rear lamp functions for the extra safety, and it also shuts off those pesky PDC sensors (only) in the rear when plugged into the trailering harness. Yes, it was not cheap. I picked up the harness while traveling in England, where it is made.