> In what way, if supplied by the bank and used only for contacting the bank to do banking, could a device become a spy instrument?

Here's my attempt at future history: Firstly they'll require you to prove your current location, to ensure that the request isn't made by a remote hacker; they'll do this by integrating their own cellular modem, as well as scanning local wi-fi networks. Then, at a second phase, they'll integrate a camera and microphone to perform a face identification, asking you to speak out a particular phrase while performing a particular motion. At the start they'll only require you to turn the mic and camera on during active usage, but eventually they'll say that these have to stay on continuously so that they can ensure that the device wasn't tempered with. And if we aren't careful, we'll accept every single small added requirement, until we're boiled alive.