maemo.org - Talk - FM transmitter

RFID is NOT RDS. RFID normally modulates and retransmits an externally generated signal.

It normally doesn't by itself transmit a signal. Of course there are applications where the RFID 'tags'/devices will emit constantly or triggered by an external signal. But in terms of volume, this is very small number.

Also, RFID is using different frequencies, not able to be provided by our N900 FM transmitter :

Quote:

Low-frequency (LF: 125–134.2 kHz and 140–148.5 kHz) (LowFID) tags and high-frequency (HF: 13.56 MHz) (HighFID) tags can be used globally without a license. Ultra-high-frequency (UHF: 868–928 MHz) (Ultra-HighFID or UHFID) tags cannot be used globally as there is no single global standard. In North America, UHF can be used unlicensed for 902–928& MHz (±13 MHz from the 915 MHz center frequency), but restrictions exist for transmission power. In Europe, RFID and other low-power radio applications are regulated by ETSI recommendations EN 300 220 and EN 302 208, and ERO recommendation 70 03, allowing RFID operation with somewhat complex band restrictions from 865–868 MHz. Readers are required to monitor a channel before transmitting ("Listen Before Talk"); this requirement has led to some restrictions on performance, the resolution of which is a subject of current research. The North American UHF standard is not accepted in France as it interferes with its military bands. For China and Japan, there is no regulation for the use of UHF. Each application for UHF in these countries needs a site license, which needs to be applied for at the local authorities, and can be revoked. For Australia and New Zealand, 918–926 MHz are unlicensed, but restrictions exist for transmission power.

Source: Wikipedia

Of course a lot is possible if you design/control also the RFID reader side and you stay in the 'FM radio' frequency band covered by the transmitter chip. But I guess you're on your own then ...