We love using tablets at our games with roll20. One issue we ran into, however, was that when you are using the measuring tool, your finger covers the measurement. When you remove your finger, the measurement disappears (as it's supposed to). Two possible solutions: 1) display the number in another location (on the line, point of origin, or just in the corner) so that it's not covered up. or 2) make the measurement sticky so that it doesn't disappear when you stop touching the screen. this would really hurt anything, as long as it disappeared when you start measuring something else or clicked on another mode.