A free app for Android, by JindoBlu.
If you want to learn how to draw hands, this 3D poser app is perfect for you. It has a bunch of pre-made poses that you can choose from. Once you select one of them, it will allow you to draw the hand in different positions and forms. You can also create your own poses and share them with other people.
The free version of this application is a little limited. It can only draw a limited amount of figures and it cannot save the drawings. If you want to unlock the full version, you can buy it for a small amount of money.