Methods and apparatus for localization, diagnosis, contact or activity detection of bio-electric tissue providing improved sensitivity to the distance between a sensing electrode and bio-electric tissue and providing the means to measure the impedance of the tissue between a sensing electrode and bio-electric tissue. In accordance with the method, a controlled effective input impedance is provided to the monitor, which input impedance can be set to cause a significant portion of the bio-electric tissue signal to be dropped across the tissue between a sensing electrode and the bio-electric tissue when the two are separated by a predetermined or arbitrary distance. Various illustrative embodiments and forms of construction are disclosed.
