Sadly, a number of devices do not support DisplayPort Alt Mode for their USB-C port (looking at you, Google, with the Pixel devices).
I would like to have an alternative mode option for these devices, where, instead of providing direct video output, would instead communicate over a custom protocol (which USB allows), sending images, text, etc. to work as a heads-up display, possibly combined with an IFTTT-like system to decide what is being displayed. The behaviour would be then similar to how e.g. the original Google Glass operated - a small display overlaying static information (with no 3DoF tracking or anything) the field of view of the user.
This mode would be especially useful if the same protocol could be established over Bluetooth as well - allowing a small BT controller and battery to be plugged into the glasses, remotely connecting to a phone, displaying relevant information (e.g. directional info from Google Maps, music playback status, notifications, etc.), while also expanding (limited) support to practically any smartphone that can use its USB-C port in host mode.
Programmable displays aren’t really new, there’s plethora of frameworks for microcontrollers like the ESP32 that allow the device to take over the heavy load of drawing, allowing the client to send just raw data to be displayed.