Modern cars are a mobile electronics/computer network.All the various control systems work together to make a safe handling car.By fitting a non Audi tow bar system,the Esp/abs system could be compromised .When the trailer is plugged into the tow socket,the electronics adjust the programme to the abs/esp system for optimum stability.Also the rear parking sensors are disengaged.I very much doubt is any after market system will do this.Any additional non approved wiring would be a good get out by Audi if there was any related warranty issue.hth

There are lots of after market tow bar fitters. Ring some and ask if they anticipate any problems. Many will give you a guarantee against any failure with the electrics or the mechanics. If I can have tow bars fitted to brand new Mercs without problems then yours shouldn't be difficult. Ten to one they will fit the same brand tow bar as Audi, adjust the electrics and save you several hundred pounds in the process. As long as the tow bar is fixed to the approved strong points and is a certified bar from a major maker there are no safety implications at all. No car maker makes their own bars, they buy them in from the few major makers, sometimes having their own name put on them,often not.

I'm sure it will be fine.