In this paper we present the ability of dry electrodes in long term monitoring of ECG, EEG and fetal ECG. We introduce the development and broad applications of circuits for wearable bio-potential sensor systems using dry electrodes enabled by the use of a high impedance FET based amplifier circuit. This overcomes the significant barrier of gel based contacts and results in electrodes that are capable of continuous monitoring for 48hrs and fetal ECG as early as 11 weeks. These electrodes will aid the development of home health monitoring systems and open up new areas for biopotential recording.