  I present a weak lensing sensitivity estimate for upcoming high redshift
(epoch of reionization and beyond) 21cm surveys. Instruments such as PAST,
LOFAR and SKA should be able to measure the weak lensing power spectrum to
precisions far exceeding conceivable optical surveys. Three types of sources
are detectable, which include the re-ionization stromgren spheres, large scale
structure, and minihalos.
  Tomography allows the measurement of the time evolution of the dark matter
power spectrum. Raw sensitivities allow measurement of many cosmological
parameters, including dark energy, neutrino mass and cosmic equations of state,
to percent accuracy. It also has the potential for inflationary gravity wave
measurements.
  Ultimate limits may be achievable through radio observations of 10^18
minihalos. Inflationary Hubble parameters H_I down to 10^-9 M_Planck can be
detected through this effect. Second order effects may also be observable,
allowing tests for backreaction and the quantum mechanical origin of
perturbations.
