I know this can be done, as the simple 15 dollar china OTA DVRs and even my TV have this. It appears that the signal strength shown on the Tablo is static, and only shows what it was at time of last scan. Since signal strength comes and goes, it would be nice to know what the current signal strength is when watching a channel. They know what the signal strength is when you tune into a channel, so it just has to be displayed. Such an option would also be handy in pointing of the antenna.
Thanks