Very cool. If someone is looking for a device with even better battery life: I created something similar -- albeit with a different approach to its visual appearance.
I would love to buy it if you can provide a way to push the message.
Can you also use it to send real-time messages ?
You can configure it to poll for messages on a fixed interval. Pushing is not possible since it would sacrifice the battery life.
What if you could build this product but to also allow for the direct power supply connection ?
There is a micro-USB connector on the back which you could just permanently hook up to a power supply. When the battery life is not part of the equation anymore, making push available is not a problem.