Never heard of it, But I googled it just now. Looks like I’m 11 years too late to the party. 
Also looks like you did the CityKnife 3 too.
But exactly what I thought the cross between the two concepts would be. But good to see that the concept would in fact work.
Looks like theres even a pair on eBay right now
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=390896634306&fromMakeTrack=true&ssPageName=VIP:watchlink:top:en
Side note: Just noticed I joined this site 9 years ago.