  We present a prospective work undertaken on Spectro-Polarimetric
INterferometry (SPIN). Our theoretical studies suggest that SPIN is a powerful
tool for studying the mass loss from early type stars. Based on Monte Carlo
simulations, we computed the expected SPIN signal for numerous hot star
spectral types covering a broad range of geometries and optical depths. The
SPIN technique is based on the detection and comparison of the fringe
characteristics (complex visibility) between two perpendicular directions of
polarization. In particular, we demonstrate that the SPIN technique is very
sensitive to the beta parameter from the so-called 'beta velocity law' for
optically thin winds. Moreover, the location where the bulk of polarization is
generated can be defined accurately. The required sensitivity for studying main
sequence OB star winds is still very demanding (inferior to 0.5%), but the
signal expected from denser winds or extended atmospheres is well within the
capabilities of existing interferometers. The visibility curves obtained in two
perpendicular polarizations for LBVs or WR stars can differ by more than 15%,
and their corresponding limb-darkened radii obtained by the fit of these curves
by more than 35%. The signal expected from the extended circumstellar
environment of Be stars and B[e] appears also to be easy to detect, relaxing
the required instrumental accuracy to 1%. For these spectral types, the SPIN
technique provide a good tool to extract the highly polarized and spatially
confined envelope contribution from the bright star emission.
