  Cold atoms are excellent metrological tools; they currently realize SI time
and, soon, SI pressure in the ultra-high (UHV) and extreme high vacuum (XHV)
regimes. The development of primary, vacuum metrology based on cold atoms
currently falls under the purview of national metrology institutes. Under the
emerging paradigm of the "quantum-SI", these technologies become deployable
(relatively easy-to-use sensors that integrate with other vacuum chambers),
providing a primary realization of the pascal in the UHV and XHV for the
end-user. Here, we discuss the challenges that this goal presents. We
investigate, for two different modes of operation, the expected corrections to
the ideal cold-atom vacuum gauge and estimate the associated uncertainties.
Finally, we discuss the appropriate choice of sensor atom, the light Li atom
rather than the heavier Rb.
