Investigated this too for several applications. For the technology (2-3 colour with slow refresh by comparison to others) my thinking was the wireless advantages of LoRa with locally stored message data. Very thin application to use standard reply widow to call messages and rough (+/- a minute or two) synch timers. Hot desks, hotels, hostels, sleeper trains to name a few is a give-away but you see where I was going…
exactly… the idea is not new off course, but to combine these ‘no power’ displays with lowpower LoRaWAN creates possibilitys,
imagine a (chain) store with e paper price tags, LoRaWAN controlled, not for clothes but for TV’s/washing machines ect.
So the headoffice can remote change all the price tags in the whole country in every shop at the same time 
a light level geolocator, a device that deduces its location in a very interesting way: by recording the ratio of light and dark in a 24-hour cycle. It’s a reverse calculation of sunrise and sunset (where you would need to know your coordinates). This takes date, sunrise time, and sunset time to calculate location.
We missed the boat here already! This is already done and dusted but as there is generally a very robust internet connection to the retail outlet no need for LPWAN of any flavour.
I met with a former colleague to discuss and this is used in retail pharmacy chains already but with Zigbee (I am pretty sure???) mesh type communication to/between the displays. Special offer goes live in 3 countries at the click of a mouse…
but there are many other uses in and around the house/office , combine it with IFTTT and see it as an electronic sticky note for example.
… and don’t ask me why I have a bunch of these at home. I’ll give you live monitored wearable equine health node with live(ish) display of what ever is important in the stable/stall/truck. Moves with the subject so not hard installed. We have a massive and very wealthy bloodstock industry in Ireland.
