The biggest difference is that the GVG vapes by way or hot air, not direct contact with flame as the healthstone products do.  I've used both and prefer the GVG as it does not burn the cannabis oil/wax but gently heats it and vapes it without burning it.  Burnt cannabis oil/wax tastes bad and is pretty harsh on the lungs.  I would assume this would be the same for spice as you would not want direct contact with a flame, but instead to let hot air to do its thing.  My guess is that some smart people out there will be able to rig something similar to how the GVG works - flame to stone heating the air and the substance beneath the stone vaping by hot air and not direct flame contact - with some or all of the healthstone products.  I have suggested to the company that markets the GVG and regular VG products that they come up with a device like this for people who want to attach a GVG head to a water pipe or erbo pipe or some other smoking/vaping device.  This would be a great addition to their product line IMHO.  I think the company that sells GVG's also sells a replacement stone (carbide foam) for around $20.  Perhaps the healthstone company could also start experimenting with using their stone at the top of the glass and allowing the substances to be vaped to go under the stone to benefit from hot air instead of direct flame contact.