  Although white dwarfs are believed to be the end point of most stellar
evolution, unlike main sequence stars, they have not yet been the subject of
dedicated time-domain surveys for exoplanets. We discuss how their size and
distinctive colour make them excellent targets for wide-field searches for
exoplanets. In particular, we note that planets of Earth-size can give rise to
multi-magnitude eclipses of massive white dwarfs. Such a large signal is almost
unmistakable and would be detectable even with very low-precision photometry.
For objects of smaller size, the high accuracy photometry currently being used
to detect Super-Earth and smaller planets transiting Sun-sized stars, is
capable of revealing minor planets down to R~100km as they transit white
dwarfs. Such observations can be used to test current evidence for
asteroid-size objects being the cause for dust rings which have recently been
observed for a number of white dwarfs. No other current exoplanet search method
is capable of detecting such exo-asteroids. As an initial test of this search
strategy, we combine synoptic data from the Catalina Sky Survey with
multi-colour photometry and spectra from the Sloan Digital Sky Survey to search
~12,000 white dwarf lightcurves for eclipsing events. We find 20 new eclipsing
white dwarf binary systems with low-mass companions. This doubles the number of
known eclipsing white dwarfs and is expected to enable the determination of
accurate white dwarf radii. Three of the discoveries have radii consistent with
substellar systems and show no evidence of flux from the eclipsing object in
their SDSS optical spectra, or near-IR data.
