I just created an awesome exercise. It's a combination of three adjacent positions of a pentatonic scale, connected by slides. The simple explanation is to play up and down the scale, sliding to a different position every fourth note.
More explicitly, sticking to three adjacent positions, starting with the lowest possible note, ascend the scale in one position for three notes. On the fourth note, slide to the next position. Repeat, sliding to the third position, back to the second, back to the first, and so on, every fourth note. When you can't play any higher in whatever position you're in when you reach the top string, turn around and descend the scale. Just keep sliding between positions every fourth note. Ascend again when you reach the bottom. It will take a few trips to complete the cycle and repeat the exact notes and slides you started with.
This won't result in strictly ascending or descending the scale. You might be ascending while sliding down to a lower position. If you stick to the pattern, you'll get exactly half of all the possible slides between positions. If you do this for all five groups of three adjacent positions, you'll cover everything.
The tricky parts are visualizing all three positions together and planning which fingers to use on the slides. The fingering for one position may not correspond to that of the next. I use my index or pinky when in doubt.
I also apply this to the other pentatonic scale in addition to the usual major/minor pentatonic.