The server currently provides robust and efficient support for synchronizing mailboxes. Check out soap.txt for SyncRequest and SyncResponse. A sync based client needs to use these requests with the other existing SOAP API's to get its job done.
The current sync protocol is light enough that you could use it for OTA (over-the-air) sync, but it would be better to encode the requests/responses as WBXML or something to the same extent (no such encoding currently exists in ZCS). For generic OTA sync we would have to add support for sync filters (sync last 7 days worth of appointments, first 1k of todays email, etc) to make the protocol feasible for devices/wireless networks.
We do not export a SyncML interface. When we reviewed the protocol we concluded SyncML was bloated for our immediate needs. One could write a servlet to export SyncML over the internal API's provided by the server (hint hint
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