Such as the N900 having an FM receiver. Although this is probably possible through software, it is nowhere near confirmed to be possible to make the FM transmitter receive just yet.
Yes, the N900 has a FM receiver hardware inbuilt. Today, we do not ship FM-radio as a built-in application. However, we look forward to the community to build exciting mash-ups of FM radio and other media experiences on Nokia N900 with high local relevance.