Low power WAN provider Helium has fired up its LongFi offering in 425 US cities, using “over 1,000” of its ad hoc hotspots to provide what could be a pretty compelling spanner in the works for LPWAN rivals. Its Unlicensed-LPWAN proposition, powered by gateways sold to its customers, could mop up a tidy chunk of the market in urban environments, and it is something that many network providers need to worry about. The business model is compelling. Customers that buy a $500 gateway are promised pay-outs in the form of the namesake Helium cryptocurrency, which is mined by the hotspots and denoted by the activity of the local network. Somewhat equivalent to a LoRa base station, or perhaps a WiFi…