I just got the Harbortronics VG-D70 Battery Grip
and it is a really nice unit. I sorely missed my D100 and battery grip, especially when using long zooms or the SB600 flash. The only negative thing I can say about it is that you have to remove it from the camera to change batteries, but it can be done fairly quickly. Of course it can hold two Li-ion battery packs so it can go a good long time between battery swaps
Besides making the D70 a lot easier to hold, it adds a vertical shutter release that is triggered using the camera's infrared port. Harbortronics also offers a camera body mod to allow a jumper cable (wired) to directly operate the shutter as well.
All in all, this is a nice little $165 accessory to complete your D70 system.
The folks at Harbortronics are also going to make this grip for the new D70s and it will plug right into the camera's remote port.