I will give you my take on the Apple Graphics Tablet: cool peripheral with little practical application. I bought mine many years ago on fleaBay and lucked out with a complete, working, and pristine tablet surface. Most that I've seen are missing something (usually pen or interface card) or have the tablet surface scored/worn.
I bought mine to play around with programming it. Even that is surprisingly difficult due to the way the tablet only properly functions when it is running code out of its ROM space. Yeah, weird. So you have to use the published API, which is pretty brain damaged, or figure out how to call directly into the ROM routines to do what you want (luckily the ROM code is published).
There were a few programs that supported the Graphics Tablet, the most interesting looked to be DazzleDraw. However, even that requires a 128K Apple //e or //c. Out of luck running DazzleDraw if you have a ][ or ][+.
So unless you are able to find a nice complete system for a reasonable price, I would look for other peripherals. This thing is also pretty large. If space is tight (and if it isn't, it will be after finding more equipment) then you may want to look elsewhere.
But it does look pretty cool.