Determination of jurisdiction for infrared products can get quite complicated but in the case of infrared motion detectors it is not difficult at all. Two federal agencies (other then Customs and Border Protection) should be thought of when importing similar type of product: Federal Communication Commission (FCC) and Food and Drug Administration (FDA). To distinguish the difference in regulatory oversight think in terms of electromagnetic (EM) spectrum. It is the is the frequency range of electromagnetic radiation with wavelengths from thousands of kilometres down to fractions of the size of an atom. Its range includes radio waves and infrared waves. Former is regulated by FCC and the latter, in some circumstances, by FDA.
During my tenure with regulatory compliance department for one of the large retailers, I noticed that a customs broker have been requesting and filing FDA 2877 for each motion detector with infrared censor. Customs broker has also been incorrectly using product code 89ILY, which is a medical device. FDA 2877 is required to be filed for each imported electronic product subject to radiation control standards. The table in 21 CFR 1002.1 gives the list of products subject to the performance standards. Since infrared motion detector is not listed in the table (directly or indirectly) and is used for non-medical purposes it is not subject to the performance standards and FDA 2877 is not required. Customs broker needs to disclaim these type of products.
FDA Electronic Products Branch Office of Communication, Education and Radiation Programs Center for Devices and Radiological Health confirmed this position. They can be contacted at 240-276-0269 if you have any further questions. Yet, some of FDA offices at various ports of entry may be of different opinion. If you, as an commercial importer or a customs broker, find yourself in this situation you need to reserve to the most practical resolution. If it is small one time shipment, then following FDA instructions at the port is most prudent. Yet, for a large and continuous importer, going to Headquarters and following regulations as they are would be more expedient, as it reduces the amount of administrative burden on your behalf.