also a warranty on the re-map? or a full warranty on the engine and turbos?
grey area, for all tuners and not just Superchips. Make sure you get them to put it down in writing for you what they warranty. AFAIK, they won't replace the turbos and engine. Who is going to do the job if deemed neccesary? I can't see Superchips paying a dealer to sort it out. They will try to put things right if the car don't run properly. That's about it.
However, given the safety margin BMW build into their cars these days, it is very unlikely things will go wrong under 'normal' driving circumstances. Most turbo failures are cause by extensive track usage and oil starvation. To date, I haven't heard of an engine failure on non-M cars that have not received some serious tuning.