As an aside, this links to a TAPR mailing list which is talking about the control head being on sale at HRO for $150. The posting was dated 12/25/10 but today (1/2/11) I can't find it on HRO's website.
Apparently the control head for the Kenwood D710 radios can be bought seperately because you can buy the radio without the APRS functions. The TNC and APRS logic are both in the control head so just buying the right one and adding it to the radio will let you add that functionality in. The interesting part comes Here. With the right cable, you can plug the head into any radio to decode APRS packets, even an HT! (Thanks to Bob, WB4APR for detailing this)
Apparently it's even still possible to connect the Kenwood AVMAP device to show the icons on a map.
CONCLUSION: On long trips, no matter where you are, we hope you will see not only one of these recommended voice repeaters on your screen, but also the nearest IRLP or EchoLink node as well... This combined with APRS Voice Alert will guarantee that if there is someone nearby wanting to chat, we will find each other.
I've made the mistake of believing APRS is for tracking only in the past. I think it would be far more useful if people would use it to advertise local services, such as repeaters and echolink nodes. Mr Bruninga really stresses this on his website and I really respect that.