Television, yes we have a maxi-cosi car seat but our 10 week old son screams his heart out in the back seat so we wanted to try him in the front passenger seat but obviously we need to deactivate the airbag first. I am aware that MB sell their own car seats with transponders built in that deactivate the airbag but we didn't want to go to that cost as our car seat fits our pram system as well. The other option we have is to purchase the transponders from e-bay but I would rather do it properly if possible.
I looked into this ages back as I had the same problem. To summarise - turning off the airbags would create a risk for any future passengers in the vehicle. Who is to know if you are buying a new car and someone has not turned off the airbag - it could result in mega litigation. Thats why MB don't provide the option of just simply being able to turn them off. You can buy the transponders as you say off ebay and some people wisely fix/sew/stick them to the non-MB baby car seats - rather than risk having them loosely in the car and thus turning off the airbags when they are actually needed. Alternatively buying a 2nd hand MB seat and extracting the transponder may be another option - but ensure the one you are buying will turn off the airbag of your MB model first.
I bought the maxi cosi - cos it can be removed and the child left undisturbed - so I know how you feel.
Personally I made the decision that if the child is crying and they are in the front passenger seat - then it is highly likely the driver's attention will not solely be on the road. Better to have a screaming kid in the back than one screaming and in an accident. I havent even bought one of those mirrors you can fix to check the child for the same distraction reasons.