Low cost: ideally the device is affordable to the end client. This may or may not be the end user.
Frequency-based: Can you provide any further context; what is the application/market? In the biosensing arena, this could be either an impedance based device (electrochemical impedance spectroscopy (EIS), dielectric spectroscopy, capacitance meter), surface acoustic wave (SAW), quartz crystal microbalance (QCM).