Syncing data with a Drupal website and a smartphone . . .

This is a repost of my forum question over at http://drupal.org/node/463040. I suspect there might be a bit more interest in this topic here, however.

I'm currently doing some research into the feasibility of the title. Basically, I want to be able to synchronize PIM data (and maybe other things?) with various smartphones, like the G1, the iPhone, various Blackberrys and Palm devices.

I found modules and discussions about various things like remote administration and making websites smartphone friendly, but none about syncing data.

I'm guessing that I will probably be looking at some sort of app for each smartphone I want to support, having them sync with some module like the Services module on the Drupal website.

Has anyone done or looked into doing anything in this area? Is there a particular direction I should be looking into to make this happen?