knife bootstrap --ssh-user pi -t template <node ip>
(this relies on you having Chef installed,
gem install chef will probably work)
Your clock will now check for new Wen code every five minutes, and download and install whatever it finds.
This is all intended to run with Chef Solo, to avoid the need for me to run my own Chef server, but I still need to be able to get updated cookbooks out to clients. I wondered about Heroku, or even serving them up from my VPS, but it occurred to me that Github Pages might be just the thing.
So I now have a Rake task which packages up the cookbook into the form expected by chef-solo, then publishes to the gh-pages branch. The cookbook looks here for any updates on every Chef run, and I somehow seem to have lashed together a Tesco Value Chef Server.