I've had great success with Night & Day contacts: http://www.airoptix.com/contact-lenses/ ... aqua.shtml
They supposedly can be worn for up to 30 days continuously without removal, but in practice I've worn them for about a week at a time which is plenty.
The main problem with these is that they don't correct for astigmatism, but this shouldn't be an issue while outdoors, and I also have a pair of cheap glasses that correct my astigmatism if I have to wear them in town.
I use AirOptix solely these days. For me, the 30 day limit is not even close to reality, I have worn a pair continuously for over 3 months, without taking them off, and ended up using the same pair a few more months after that.
But I would suggest that you try them out in normal circumstances, first. My eyes seem to adjust exceptionally well to contact lenses, but some of my friends cannot wear even those lenses for more than a day.
I have been using them for at least 4 years now, and my eyes have periodically been checked by a doctor. He was a bit horrified about the length of time I keep using them, but since both the lenses and my eyes seem to have no problem, he told me not to worry.
Even still, I always keep an extra pair in my backpack.