It wouldn't be the most important aspect of such a hardware wallet (maybe TEMPEST is a consideration?). These wallets (Trezor and Ledger Nano S) generally get their power via microUSB connection, and they're not on a lot like a wall mounted weather app would be basically 24/7 on. The Ledger Nano S uses OLED according to themselves [1]. If there's a way they draw less power, that is welcome if the source is say a laptop. There's also the Ledger Blue which uses a (larger) color touchscreen and rechargable battery. For the price of almost 4 Ledger Nano S.
I see main utility when you need per-item/per-transaction billing.
Instead of having to print static-per item tags, or redirect users to a website with online checkout, you can have that thing to generate individual codes for each piece of merchandise.
If you're scanning the bar code with a phone app, it's just going to use the camera. So as long as the display has a high enough resolution to display the QR code and it shows up on a camera, it should work fine.
But keep in mind, you probably want the device backing the epaper display to allow some kind of password input and store your BTC key on an encrypted medium (either encrypted flash or an LUKS/ext4 formatted sdcard).
No, the display technology doesn't matter. It would make sense if you want to send transactions through QR codes, might be an interesting project. Not sure how it would be more useful than a Trezor, though.
