These are all great additions to enhance the passenger experience and will result in more reviews and tips.
I also provide these things and some individually wrapped candy. I've been thinking of a way to get a small water dispenser and some plastic cups, it might be useful.
I do the same. I always offer items within the car if anyone needs them. I keep those small chip bags handy along with candy and bottled water. Some people have medical conditions that may require them to get something in them to feel better so I like to be helpful.
I really don't buy the idea. It is definitely bad for your phone, you may try the nano type phone mount, it is pretty good! In Apple's Case Design Guidelines, there are sections on Sensor Considerations and Magnetic Interference, including the line, “Apple recommends avoiding the use of magnets and metal components in cases.
These are great things to have in your car to make people more comfortable. I used to offer snacks and drinks but people were getting too greedy with them. One woman took 8 water bottles and stuffed her purse full and then denied doing it. I was so angry. I stopped offering things.
I just keep water bottles and saltines on hand. I do have two chargers as well for iOS phones and Android phones. A lot of people make use of those.