Mcollective has been able to fire up puppetd runs for a while now, via a standalone RPC call or through the puppet commander binary (check it out, spread your load). I wanted to be able to fire up my chef clients with mcollective, to use metadata to filter what should be impacted. So I wrote a little piece of ruby, mostly based on the puppet one, to achieve this. You can now do the following :

mco rpc chef runonce or  mco rpc chef status

The plugin is available on my github mcollective repository.