For the reference: all those criterias are satisfied except one: "It should be designed so that the nothing can alter the radio
modem's own software. This program must not be updatable."

It is upgradable and we fail to see any reason why it shouldn't. Every possible threat about backdooring the device will be still present even if upgrading is somehow blocked. What's more, if the modem manufacturer would give us some way to block flashing the ROM, how would we know that he's didn't put any backdoor there as well?

We believe that it's better for user freedom to give him/her the ability to upgrade the firmware. We're convinced that any effort to make sure that "nothing can alter the radio modem's own software" is futile, because it would need us to trust the manufacturer anyway - and if we would trust the manufacturer, we wouldn't have to block it at all. We're proposing tight monitoring of what modem does instead. More about that in the article

(there's also GPS integrated with the modem, but it can be blocked from software and odds are that we'll also provide an option with second GPS chip - see http://projects.goldelico.com/p/neo900/issues/526/ )

PS. Even if I won't use the pager at all, I find it really great idea!