RFID-based sensors, RFID readers and software sense a changed condition. In one embodiment, an RFID-based sensor includes a base that may be placed at a location where a condition may change. The sensor includes an RFID tag that is coupled to the base. The sensor also includes a detector that can be electrically coupled to the RFID tag. If the condition changes, an electrical property of the detector also changes, impacting an operation of the RFID tag. The impacted operation can be detected by an RFID reader/interrogator so as to provide a notification. An advantage over the prior art is that the condition change can be sensed wirelessly over a domain that can be laborious or hazardous to access otherwise. Moreover, RFID based sensors can be made by modifying common RFID tags.