  We introduce a new kind of non-relativistic ${\cal N}{=}\,8$ supersymmetric
mechanics, associated with worldline realizations of the supergroup $SU(2|2)$
treated as a deformation of flat ${\cal N}{=}\,8$, $d{=}1$ supersymmetry.
Various worldline $SU(2|2)$ superspaces are constructed as coset manifolds of
this supergroup, and the corresponding superfield techniques are developed. For
the off-shell $SU(2|2)$ multiplets $({\bf 3,8,5})$, $({\bf 4,8,4})$ and $({\bf
5,8,3})$, we construct and analyze the most general superfield and component
actions. Common features are mass oscillator-type terms proportional to the
deformation parameter and a trigonometric realization of the superconformal
group $OSp(4^*|4)$ in the conformal cases. For the simplest $({\bf 5, 8, 3})$
model the quantization is performed.
