hi Ladydriver! Here's a start for the tool. It's well worth the investment!
You can also search EBAY for a used or new tool as well. http://www.bimmerzone.com/BMW_SRS_Airbag_reset_tool.htm
Also, before you buy a tool, go the Motor Vehicle Department of your locale or its website and look for EXACTLY what is to be inspected. In my state, it is basically, emissions, tires, brakes, lights but nothing on the airbag light. The concern is faulty equipment that can cause accidents and harm to others and environmental issues as well as your safety.