A lot of pros who use their laptops in the field have to power down or plug in between swapping batteries. Often, this happens multiple times a day. It's time consuming, and well, I'd love it if a professional grade laptop had a small battery, maybe 100ma or so, that could keep your laptop powered up during live battery swaps.
Actually, the external battery pack pictured above probably wouldn't do — I don't need this to a full rating to also charge the laptop — it just needs to be enough to keep it running for a minute. I know there are laptops that have slots for second cells, and extended battery packs, but I don't need anything so drastic or heavy or large. Just keep me up as I switch cells. First manufacturer to make this gets a cookie. PS Hibernate would work, but I'd like to keep network connections and uploads and downloads still going at the same time.