DVR diagnostics with signal strength, SNR, RS uncorrected and corrected is very beneficial in fine tuning the antenna. And it does two stations at the same time, very beneficial if you have a difficult installation.
It would be grand if TiVo put the DVR Diagnostics on the iPad app. This could save a person many hours of work and a lot of dollars.
Not a TV but certainly portable. There is an Android app that can read that data from a SiliconDust HDHomerun or you could connect an HDHR to a win7 laptop or netbook. That would give you signal strength, signal to noise and symbol quality. Not quite an actual error count but similar information.