The Short Version
Multiple peer-reviewed studies and industry sources confirm that ammonia-detecting smart stickers have been successfully demonstrated as non-invasive food freshness monitors, particularly for protein-rich foods like meat and fish. The claim's "can be used" framing is a capability statement that the evidence clearly supports across several sensor types (colorimetric, graphene-based, NFC-enabled). Most implementations remain at prototype or early commercialization stages rather than widespread consumer deployment, and real-world performance can be affected by humidity and cross-gas interference.