I have a software/hardware package from Teletype company that I run on my laptop and my Compaq iPaq. It was difficult to learn how to use, the directions were not very good. Now that I know it well, it works well.
Long learning curve but works great. You can learn more at www.teletype.com
I would love to have comand in my C Class, but it was not available when the 203 first came out. They also were honest and told me that it could not be easily retrofitted.