no offense but mediawiki's search function is really bad. I normally use google to search wikipedia, with a "site:en.wikipedia.org". But since en.m.wikipedia.org has nofollow noindex, google doesn't work on it. I understand that you don't want normal web traffic to flow into the mobile site, but there must be a better way.
Ok so maybe the solution might be different, like: redirect people based on user-agent and cookie/prefs. So that mobile users get the correct site even while visiting from the standard url... (Having not yet tried it from a phone or kindle, I am not sure what the current behavior is)
-ALok