Its 111x60x31mm so a bit of a beasty but I'd rather a tidy big mod than a messy little one.
That's about the size of a Hammond 1590B.
I do not think you will be able to read the resistance through the Escribe with just USB power.Normally your resistance is 0 until you hit fire button.
It does power the screen on(very handy to check you have not screwed up screen install).