[aprssig] Low power APRS digi that allows additional data

[Jason KG4WSV]

To clarify the OT2 line a bit, the T2-301 is a T2 built in to a radio.
 The OT2m is a standalone TNC.  I'd suggest taking a look at the OT2m
TNC, as it's got quite a few features.  It may have enough features
that you don't need to add an additional microcontroller to get your
data gathered and transmitted.  It's also a smarter digi than pretty
much anything out there that doesn't require a PC to run on.

-Jason
kg4wsv