You can already by a 13 inch mobile e-ink monitor. There's the Onyx Boox Max series starting with the Max2 (the current model is the Max Lumi) with HDMI in and

You can already by a 13 inch mobile e-ink monitor. There's the Onyx Boox Max series starting with the Max2 (the current model is the Max Lumi) with HDMI in and the Dasung Paperlike monitor. They are pricey, however.