Having seen a few requests for CALDAV and CARDDAV synergy connectors (and indeed wanting them myself!) I decided to get the ball rolling:
Attached is a mauled version of HPs example plaxo connector that kind of works with (the only one that I've tested) CARDDAV server -so it inherits all of the restrictions that that has and has a lot more that I've caused too (notably it won't get contacts from subfolders at the moment). And it still calls itself Plaxo because I haven't gotten around to changing it yet.
Please note that this is very much alpha (or probably not even that good) and at the moment you have to edit the serviceEndPoints.js
to put in the server URL (So you have to have the SDK installed, then run buildpackage (included in my zip file) and it'll install it in the emulator.
Given all that, I wouldn't recommend installing it on a phone, but if anyone else is interested in helping, and wants to run it in the emulator against some different CARDDAV servers, I'd be interested to know if it works (at all). I'd be even more interested in fixes that people can suggest!
And despite all the above, it has managed to successfully download my address book from my CARDDAV server!