The Scrubbing Bubbles Automatic Shower Cleaner (SB ASC) has been a Godsend to my parents household. It is a device that you hang from your shower head and place a bottle of cleaning solution inside it. You can use it however often you like, I believe the package recommends once a day. When you get out of the shower just press the button on the front, it'll give you a few seconds to get the door shut or the curtain closed and then it will shoot a stream of cleaner around your tub and shower. It really cuts down on the amount of time you will spend cleaning your shower.
My parents live in an area with very hard water and the water also has a serious rust problem. After just a couple of showers their shower needs to be cleaned badly. The walls and tub are so discolored because of the water and the only thing that would get it clean is very harsh chemicals that smelled horrible. It was also hard for my mom since she has arthritis and the constant spraying and scrubbing so hard really hurt her hands and fingers.
I got a SB ASC for myself and I really loved it. I thought that it might be something that would help my mom not have to clean their shower so often so I got one for my parents. Since their water is so bad I suggested they use it after every shower, not just once a day. It helped even better than I imagined it would. My mom cleaned the shower before we put the SB ASC in and used it after every shower. The results were that she didn't have to clean the shower again for 3 weeks! It really helped keep the rust from building up and when she did finally need to do some touch up cleaning it was not nearly as hard to get clean as it had been in the past.
The price above is for the started kit, which comes with the device and two bottles of solution.