A better stylus for interfacing with touch screen devices, iphones & ipads eg

I want to brainstorm a problem I'm having. The need is the development of original technology that will help people like me (I have Parkinson's Disease) navigate efficiently on touchscreen devices such as iPhones, iPads, or other Android devices. To be specific, people who have tremors find it difficult, if not impossible, to navigate due to the touch sensitivity of the device and the hand movement required to get the desired result. While there are many pens available on the market that have a stylus built into the nub, this still requires a deftness of touch that makes using this type of pen less than desirable. One solution is a product that will roll over the screen, allowing for free interfacing with the data on the page while not triggering the page to constantly change screens. My question is, is this type of tech already available? Would it even work? Who can help me with this ?