This is a site I came up with so I can always throw Poké Ball straight. I hate it when I waste half my Poké Balls trying to catch a pokemon. This greatly improves your accuracy. This is a plate so you can use it over your phone case and on any phone. The large circle is so you can throw curved Poké Balls. before throwing the ball make a circle around the Poké Ball and it will start to spin then throw straight up the screen.
Note you still have to judge the distance but it has really improved my accuracy.
Be sure to checkout the new makerspace http://inventorforgemakerspace.org. There are guys there that have made some incredible 3d prints.
This is an easy print its a plate. Prints in about 10 minutes.