I think it has some potential if you're using heavy mountaineering gloves, sometimes things only become apparent when you use them.
As far as accidentally switching on and off by walking into things, you have to be really close, like an inch or less, rather than just 'near'. I don't know how it'll cope with heavy rain/snow/fog, but I've got my fingers crossed for some really unpleasant weather - which sounds very wrong, but you know what I mean.
And yes, will keep an eye on battery life in real world conditions.