A magnetic waveguide atom interferometer is a device which creates an interference pattern by coherently splitting a Bose-Einstein condensate (BEC) into two separate parts, guiding each along separate paths using magnetic waveguides, and recombining them at some point later, resulting in interference between the two pieces of the condensate. Such a device is sensitive to the relative atomic phase between the two condensate pieces, and is therefore sensitive to the difference in path lengths traversed by the two condensate parts. A separated-path atom interferometer can detect anything that alters the condensate phase or path traveled, including inertial forces (such as gravity, gravity gradients, and rotation), magnetic fields, electric fields, and relativistic effects. There are a myriad of applications to inertial force sensors, particularly involving the detection of topographical features that have densities different from surrounding areas. Applications include navigation, object avoidance, detection of underground oil and minerals, corrections to the orbits of Global Positioning System (GPS) satellites, detection of subsurface structures such as tunnels, precision tests of general relativity, and searches for new fundamental forces. Atom interferometers are robust and potentially inexpensive devices for these applications, as they have no moving parts and can be built with commercially available technology. Waveguide interferometers add the benefits of extremely high sensitivity coupled with compact size.