It seems odd to me that by default the virtual keyboard is at the bottom of the screen seeing as your thumb naturally rests towards the top of the screen.

Is there an app that will launch the virtual keyboard at the top of the screen for all applications that prompt the keyboard?

Not that I know of. But I must say, I think the opposite is true - it sometimes seems odd to me that the start menu is at the top. We must hold our devices differently, but I am a big guy with large, goofy, basketball-palming hands and I still hate constantly stretching to the top corners.

And yes I know there are apps that move the Start to the bottom - didnt like them. Now I just use the windows HW key at the bottom.

I would imagine it is fairly easily doable by way of registry edit, but I am guessing you will have a hard time finding an example. Hope you do though - good luck.