The U.S. FCC has reallocated the frequencies used by the analog Tele-Aid system in early 2008, and MB is discontinuing its analog Tele-Aid service by February 2008, according to correspondence I had with them.
With respect to Tele-Aid, Wolfgang has posted some information on an analog-to-digital upgrade for older cars. I don't know how this upgrade will affect the equipment required as discussed here, if at all. See
Wolfgang's Telematics page. One contributor has reported that he had the Tele-Aid upgrade done; Cost for the new Tele-Aid unit is $600; plus $294 for 1 year of service; or plus $548 for 2 years of service. These are MB MSRP, but the dealer is free to set its own price. Prices do not include labor.
The MBUSA website indicates that some MY '00 S-Class cars may not be able to be retrofitted; others may be able. Later models can be retrofitted.