I have actually been following this as well, and I have tested several
of these handsets. Others have been impossible to source. Typically
startups will attempt to bring a wifi voip handset to the market,
realize there is no demand, and fold.
In the particular discussion of WPA:
Note that the two Senaos listed claim WPA support, but this is not
available in the current firmware. There also hasn't been any updates
to it in a year or so -- don't expect it anytime soon.