Any sensing method needs a technology to be realized to be a real component. Typically there are many technologies even to the same sensing principle. And for the same sensing application there can be many sensing principles. Mostly a sensor component user does not need to care about technology, at least a mobile device user does not care.
But when you are selecting the right component for your application, or you are looking a sensor for your new product, or just comparing components, it is good to be aware about technologies.
For example, a magnetometer or electrical compass:
A magnetometer is used for motion sensing together with an accelerometer. Now there are solutions which are extending its use to traditional gyro applications. So it possible to replace a more expensive and power hungry gyro with a magnetometer when you select the component and technology right.
The technologies for current magnetometer components are: Hall, AMR, GMR, TMR, MI, and Fluxgate. You can find all them used in current devices. One interesting aspect is that typically one supplier uses its own one technology. Thus when you select a component and supplier you select the technology and vice versa.
MobileDeviceSensors.com will list and compare sensor technologies for you.
Please, contact to get the updated list of technologies, components and providers.