Not had an issue to date with tuning boxes, and ran both my wifes, last couple of Golf R's with them - Both had warranty work, and nothing came back. Im sure manufacturers are changing their detection systems all the time, but we've had no issues to date.
We are based in Bognor Regis if anyone want to come and try one out, I think you will be pleasantly surprised - We sell 2 or 3 a month with no issues.
Sure they are not a custom tune, but they are fully adjustable, and at present they keep your warranty intact. I have a customer with a 2015 180BTDI that has done near only 80,000 miles with a box on with no issues. I've run them personally on all my vehicles for a couple of years. I was also a re-map person, but cant risk loosing my warranty.