Bidet seats do not need a hot water line, but they do need a GFCI protected electrical outlet within 3' or so.
They have self contained water heaters, seat heaters, drying air heaters, and ozone based deodorizers. They pre-mist the bowl sides when your first sit down to help keep the bowl clean. It's a pretty magnificent device. It's 25% of the way through the 21'st century, and I may not have a flying car just yet, but at least I have a robot to care for my tushy.
Prior to installing bidet seats throughout the house, we had handheld bidets that were attached to the cold water line. It's really never immanentized a "religious experience" so far as I have noted, and while the heated one is certainly more pleasant, a cold water bidet seems to function pretty well for hundreds of millions of people around the world.