A valve stem pressure poppet incorporated into a tire valve cap for monitoring tire air pressure. The indicator assembly is screw attached by a connector onto an existing valve stem. The assembly includes a hollow outer tube for housing a slideably disposed indicator, a sealed space above the indicator, a compression spring and a connector end fitting. An air passage runs throughout the length the indicator. Once the assembly is engaged, pressurized air feeds directly through the indicator into the sealed space, forcing the indicator down against the force of the compression spring. If the tire remains above a predetermined critical low pressure point, the indicator will remain in the down “equilibrium” position. However, if the air pressure in the tire drops below the critical pressure point the compression force of the spring will overcome the downward pressure on the indicator, and the indicator disengages or “pops” up.