I'll second the recommendation for the PowerTow EZ40. They've even got optional snow chains for it.
http://www.powertow.com/40ez1.html
I got the optional electric starter and headlight. That might come in handy on those long dark Alaskan winter nights.
I don't think the WingWalker is even powered. I think it's simply a geared crank system. I think your arm would get tired if you had to move the aircraft any distance at all. The nice thing is that you can take it with you in the plane. That wouldn't be practical with an EZ40.
http://www.wingwalker.co.za/wingwalker.htm