  The Stellar Planet Survey (STEPS) is an ongoing astrometric search for giant
planets and brown dwarfs around a sample of ~30 M-dwarfs. We have discovered
several low-mass companions by measuring the motion of our target stars
relative to their reference frames. We describe the STEPS method for stellar
centroiding that enables our ~1 milliarcsecond relative astrometry. We describe
one of the astrometrically discovered companions, GJ 1210B, which was later
confirmed with an imaging observation. GJ 1210 A and B have spectral types
M4-5, based on their luminosities, inferred masses, and colors.
