If you look at healthylivingdirect.com and go into personal hygiene you will find a similar device to the hospital-type bottles but these have and additional bit that converts it so that male or female can use it. I find them to be very useful and at £4.99 very reasonable.
They are great if you have a bad back, means I don't have to sit on the loo seat in the van at night which is agony if my sciatica is in full flow lol.
With regard to the Shewee - what do you do with the wee question. As I said I only use mine out and about and not on a site but you can put the output hose into a bottle so you could use an empty water bottle and then take the content to the loo.
As Snowy says other than for out and about and no facility use they are useful for those who can't squat or have other mobility type issues.
I'm afraid I got a portaloo as got it cheap in Netto for £25. OH said it was a 'waste' of money ( pardon the pun!!) but he's not the one who has to take 3 girls to the loo at various hours in the night and early morning in the 'piddling' rain and through fields of muddy 'muck!. Best £25 I ever spent!
------------- It always rains on tents. Rainstorms will travel thousands of miles, against prevailing winds for the opportunity to rain on a tent.