yes, absolutely feasible. you hoock up the pager's "ringtone" to the expansopn connector IRQ line and you need some - probably low bandwidth - interface for payload data to either the USB or I2C interface of expansion connector (not implying that either of those signals will be guaranteed to make it into our final design, for now that's just plans).
Depending on channel/band and modulation of the pager service and depending on the FMRX chip we will have on Neo900, you may get away with a software solution that doesn't need any hw-expansion.

/j