My immediate reaction was that I want one. My second one was 'what a simple device!'.
Working backwards, its fundamental constraint is it's reliance on GPRS, which is slow and typically priced in terms of the amount of data transferred. So to be economic (or to make a profit) you don't want to stream too much data. However the speeds not unlike a dialup modem, and while complex big documents were slow to transfer, simple character mode email programs such as pine worked just fine. Pine or indeed mutt are good examples - relatively simple interface and coupled with a basic editor such as pico or nano very useful.
And you don't need complex formatting to send emails. It's about text after all.
But increasingly email is sent in rich formats these days, usually html based but not always. This adds to the payload, the amount of data transferred, but not the content - what's said. Now emails are usually multi part including the mime encoded attachments and the sexy version of the email and hopefully a plain text version.
So by interposing a server that polls the users mailservers by using a fetchmail like process and then decomposing the message into its component parts, throwing away all the non plain text parts and/or stripping out any exteaneous formatting to get rid of the non plain text parts. (yes I've seen examples of message that would die if this was done to them but not that often).
Suddenly you've got a lightweight message to forward on.
As I say, very simple - breathtakingly so. You could imagine also doing a similar service based on qeu and dsl on a usb key and booting into pine.
In fact, many years ago I built something very similar.
We had a pile of old computers with limited memory, network cards and no hard disks. And we had boot roms which did pxe style requests to allow you to transfer down and execute a 1.44Mb floppy image. What I did was put an operating system on it, a tcp stack and a locked down version of kermit (actually ms-kermit and freedos) in terminal emulation mode that logged into a sun server and forced the user into pine. Logging out of the system forced the pc to reboot (basically we waited till we saw the word logout go past) to ensure a clean session for the user - basically a quick and dirty university email reading terminal - login, read mailm exit and walk away.
Peek is an enhancement of this concept, and a damned interesting one ...