The real problem with inventions is not inventing something, but
1) getting a patent that is wide enough
2) having enough money to fight those who break it
3) capital for start up (especially for mass-market devices)

1) A company holds a patent for a device that works with a 30 degree "piece of pie" cut out of a disk, a competitor cutting a 60 degree piece was held not to be in violation of the patent.
2) If you are succesful, one of the industrial giants will just ignore your patent and bleed you dry with the costs of the lawsuit you bring agaist them (I once worked for a 100 or so employee company that died that way)
3) For a mass-market device, you will need a specially molded case, a specially molded keyboard and a specially designed display. In addition, to get the price where people will buy your product you need to buy 100000 of each part to get the parts cheap enough.

If you can handle the above, go ahead and invent.

Erik