Great for wild camping with the canoe when you can't dig a hole - just need a tent tall enough to sit on it in ;) Contrary to everyone else, number twos only - a bed bottle does number 1s.
weegil - you used a pett toilet. Ours is 12 years old now, fab product, I wouldn't be without it.
Also have a bog in a bag in our weekend kit. We camp in fairly rustic places and can be some distance from a loo. They are overpriced I suppose but they are fairly sturdy and take very little room.
I 'prime' it before bedtime and in the event of me or my daughter needing it I find it a much better option than dashing across a field in my onesie.
Like PaulaMB we have a PETT which is superb. Yes the bags are expensive but if used for overnight or emergency visits are more than adequate. For the two of us a bag can be used for up to 3 nights and there is no smell.