would there be a way for the transmitter and receiver to work in tandum so that when the receiver picks up interferance it pushes the frequency of the transmitter to the next free frequency.

If the receiver worked before the transmitter the transmitter could display the frequency it is changing to via rds notify, eg 'changing to 102.2 in 5 seconds' maybe accompanied by a beep. that way youd never even have to look at your n900.