Just last week we reported that the Nest Learning Thermostat was coming to Apple stores, and now the energy-saving gadget has made its way onto Amazon. Introduced by ex-Apple executive Tony Fadell, the Nest has proven enormously popular since its launch late last year — there was a period of time where the only way to get one was to hope that the company sent you a by-invitation-only purchase link, in fact — so the move to a mega-retailer like Amazon (along with Lowe's recently) might finally signal that inventory concerns have cooled off.