Recently I come of a song with m7b5 -> V/vi -> vi and it sounds good. In both Hooktheory I and II there is little about the m7b5 chord but it is actually widely used. Anyone has any idea how it fits in a chord progression ?

The 3rd intervals of any triad determines the family that triad belongs to. Hence a m7b5 is a minor traid that uses a dim 5th. If you raise the dim 5th a semi-tone you convert any m7b5 triads into a minor triad

C Eb Gb is your C dim triad

C Eb G is your standard Cm triad