In the case of the compute stick, you could use a separate SSD to initialize the blockchain, then disconnect it. Sticking these things in every nook and cranny could be a real problem for those against Bitcoin.
So for basically to allow for p2p tx and block relaying around the globe thru smaller mediums. The main use case I woulda thought is to reduce time for new nodes to sync up.. Since we know the price of hd is falling faster then the need for that space.
The pruning stuff does not reduce sync time at all, though the recent headers-first and syncing improvements do.
In order to prune syncing you have to relax the idea of independent verification and rely on someone else telling you that the part of the chain you are seeing is valid (as with SPV nodes). That's a major change to the Bitcoin trust model.
With spv you only get headers and maybe coinbase tx correct? So you wont be able to import your pvt key and get your txs in spv mode..