A few things.
1. You cannot reset the Airbag light until the problem that triggered the Airbag light has been repaired. So do not sweat the details, there is no magic way to clear the Airbag light without correcting the problems within the Airbag system.
2. Just because you cannot find an "App" to do what you want does not mean the dealer is the next stop. Not sure why everyone thinks only dealers can communicate with the modules on German cars. Keep in mind almost ANY Indy or gas station that has decent mechanics, someone WILL have a Professional scan tool that will read ABS and Airbag systems.
3. Not sure you will find many Apps that support ABS and Airbag on these cars. There may be a very few on the market, but I doubt it. There are very few Apps that support ABS and Airbag systems. Most support Ford, Mazda, Toyota and other models. BMW and GM was a TON of money for rights to the data and some is even subscription based so the App vendor has to continue to pay for the licensing, otherwise their hard work for the App is down the drain.
4. As mentioned, BMW Scanner 1.4.0 is only $30 or so, if you have a PC laptop, install it and you have a powerful tool. If you do not want to go this route there are other options.
5. There are plenty of Consumer and Prosumer level dedicated scan tools that support other than OBDII.
For example there are many by Launch, Autel, Foxwell and Schwaben.
I would not go on the too cheap, because you get what you pay for.
Here is one option for under $70 that claims it should do what you want. I have not played with this tool, but understand this, even at $70, this is still LESS than what you would spend at a Dealer or Indy.
https://www.amazon.com/Creator-C310...&qid=1503023795&sr=8-2-spons&keywords=bmw+airbag+tool&psc=1&smid=A1R0JBJ46WBNT5
6. Tools are an investment, while you current focus is your E46 people are often very short sited. I do not know your situation, but I have a fleet of vehicle, BMW's, VW, GM and others within the extended family. So for me, I often buy more than I need for more overall flexibility of vehicles that a tool supports and resale interest and value. If the tool is E46 or BMW only, it has limited appeal than a tool that may support 32 manufacturers.
Open up your mind and think about the big picture.
