A small-scale sensing technology can be used inside pipeline maintenance pigs of any size and configuration in order to measure fluid conditions map pipeline features and identify potential wall buildup or defects. The tool can be used in pipelines where conventional in-line inspection tools cannot traverse while significantly reducing deployment cost and risk. It can also be used to provide near real-time monitoring of critical pipeline characteristics. The pill-shaped housing containing the sensing elements can collect data on multiple variables including pressure temperature magnetic field and 3-axis tilt or acceleration. Multiple tests were conducted using the technology mounted onto foam pigs in a 12-inch flow loop with single-phase gas and liquid media. Results from the sensing device consistently identified known bends and wall-thickness changes as small as 0.125 inches. The sensor pill device was also deployed in a free-floating arrangement without a carrier pig in the flow loop filled with water. This design enabled the sensing device to travel the length of the line without a pig thus indicating a potential inspection solution for fully unpiggable pipelines.