A sensor assembly includes a patch with a wall configured to be seated in a well casing. A sensor is mounted to the wall of the patch. The wall of the patch can define a central passage therethrough configured to allow passage of downhole tools therethrough. The wall of the patch can be expandable from a first compressed diameter to a second expanded diameter. The wall of the patch can include at least one of a corrugated expandable structure, a stretchable structure, and/or an internally trussed expandable structure, for example.