Electric shower heads are the most common water heating device here in Brazil.
As our weather is warm-to-hot-to-scalding 99% of the year, it seems to be a nonsense to spend lots of money on hot water pipes and a water heater.
It's very safe to use if installed correctly. It's basicly a shower head, with a shielded (AND GOUNDED!!!) electric element inside it. There are many models available from the cheapest with only three positions (OFF-SUMMER-WINTER) or fancy and very expensive models with electronic infinite controls, pressurizers, etc. The temperature fine adjustment can be made by simply opening a little bit more or less the tap.
The most famous (and reliable) brand is Lorenzetti (The inventor of electric showers). They also make electric kitchen faucets (I have one and I turn it on during the winter week) and "point of use" electric water heaters and other kinds of heaters and stuff. (how they are making metal fitting too like faucets and mixers, monocommand kitchen faucets, towel holders, soap dishes, etc)
The great about these showers, faucets and point of use heaters is the fact that they are tankless, fully automatic and heats only the water you're going to use and you never run out of hot water. You just need to open the tap to turn it on and close to shut down. The electronic control can adjust the temperature or turn the element off. It also has a differential residual device to shut it off immediatelly if something wrong happens. this devide is so fast that can activate before you feel any shock. The earlier models used to last a lot, now they last only 10 to 15 years.
My shower is one of those fancy models with electronic control and pressurizer. I opened it and disconnected the pressurizer's wires because my water pressure is so righ that I had to use pressure reduction rings when I installed it otherwise it would pop out it's plastic shower head cap.
above the tub I have an standard shower head as that bathroom has a hot water tank. Recently I replaced it by a chinese model that i bought in paraguay for only 9 dollars. beautiful and interesting design it had a ring with holes and inside it there was something that looks like a star or a garden sprinkler and spins like a dishwasher arm... Super cute, but lasted only 10 seconds after i open the tap and it broke in pieces and started spkrinkling water everywhere. I don't even know how is taking a shower like dishes in the dishwasher LOL. Now I'm back to the plain shower head that came with my apartment when I bought it. Since 1997 and hever had the smallest issue with it. it also has a metal hose with a hand shower that I always use to wash my hair.