Embodiments of the present invention provide devices (tags with sensors), systems, and methods to determine states (such as, but not limited to, complex impedance) of materials-of-interest, such as tissue-of-interest, implants, and construction members, to name a few, in a non-invasive and contactless way; and using comparatively safe and/or low energy electromagnetic radiation, such as radio waves. Negligible-sized wireless-tags with sensors are implanted in such materials-of-interest. Using wireless communication and imaging technology, the states of the materials-of-interest may be monitored; which may allow non-invasive and contactless detection of problems such as cracking, bending, excessive pressure, improper temperature, and/or the like. Additionally, initially unknown locations of the implanted negligible-sized wireless-tags with sensors may be readily determined upon a given scanning (reading) session; and thus mapped to provide an effective image of the material-of-interest.