Ah, the bum gun. Always attached to the side of the toilet within easy reach.
A key part of any trip to the toilet. I honestly don't know the real name for it, but pretty much everyone I meet calls it the bum gun. It's available in all bathrooms that have some form of toilet and running water such as gas station stops to small homes to hotels and modern houses.
It kind of makes sense, though. You don't wash off your face or hands with toilet paper, you wash them with water. Why treat your lower-region any differently? I've also used it to spray down my bathroom and toilet as a way to easily clean everything.
The first time I tried one (in Sri Lanka) I was so confused that I took off my pants just in case everything got completely soaked. It really does come down to how you angle it to spray and not have water go flying everywhere mixed in with...well, you know. When finished, you just shake off, and the water quickly dries. You aren't that soggy and the spray is not that out-of-control as I thought it would be. The only risk of using one is when you don't know how strong the water pressure is. It can be a bit of a shocking way to wake up!
I think in warmer climates, where water evaporates in seconds, it makes way more sense to use the bum gun. It saves the environment in a way by eliminating paper waste, which tends to get burned along with other garbage. It doesn't really use that much water and is probably way more sanitary in general.
I used to be freaked out by the bidet in Europe, but I think the Asians have got it right with the gun.