Lapka EMF Sensor Electromagnetic fields (EMFs) can be caused by electronic devices, wireless transmitters, or nearby power lines. Lets clear the air. Lapka EMF does not detect ghosts. Lapka EMF takes measurements of both High Frequency and Low Frequency fields and can detect cell phone antenna activity, microwaves or exposed wires. This information will reveal the spots with the least electromagnetic pollution. Thats where you might want to put your yoga mat.