LILYGO T-Echo If you’d like a device that good for hacking and comes in a small case, The LILYGO T-Echo is a simple small low-power ready-to-use handheld device for about €80. It has ~3cm square e-ink display, a case with a few buttons, Bluetooth, GPS, and about a day’s worth of battery. Input/output/charging is via USB-C (but use a USB-A to USB-C cable). Received messages are displayed on the e-ink screen and can be cycled through with the buttons. Sending messages requires connecting with another device via Bluetooth.