I was doing some searches on the MBWorld site and happened to come across this link in the SL class (R230) forum. It was dated 11/2009, but I clicked on the link and the company is still in business, so it must be a reputable operation. Based in Hong Kong but after looking through the site it appears trustworthy to me. I don't think I'm technically up to speed enough for this diagnostic tool for Mercedes, but perhaps some of you are more versed in that sort of thing. Seems it could pay for itself (although I couldn't find a price listed) with a few avoided trips to the dealership. If any of you have experience with something like this, I'd be interested in how it works for you. I wonder if this tool is what RENN Tech or Eurocharged use for ECU programming? Anyway, here's the link:
http://www.yohotech.com/products/YH311.htm

 

Costs $625. Looks like it connects to a PC and they give you a hard drive for a specific Dell laptop that becomes the terminal to operate the device.
If I were an independent shop this would be very useful.