With the 'Live TV Input Framework' along with the recently added MPEG2 hardware-decoding, the potential for the Live Channels app to be coupled with a simple DVB-T2 USB-tuner seems obvious.
However, when browsing around the web, pretty much the only tuners, people are discussing, are the HDHomerun devices. These are expensive and provide way too much functionality for this purpose. And people are reporting tons of issues with them, likely since they work through people's home-networks, leaving room for various errors...
Can it really be true, not a single such product exists, yet? In my head, I'm dreaming of a product similar to the Xbox One USB TV-Tuner.
Another option besides the HDHomeRun is the TabloTV. It's a similar device, a networked DVR with compatible Android TV app. I'm not sure if it integrates with Live Channels or not.
I've been thinking about this a lot myself, but I've found myself watching much less major network TV lately so I've put it on the back burner.
I just sold my old 2008 TiVo HD, but I absolutely became addicted to the 30 second skip button which allowed me to skip an entire commercial break in about 3 seconds or so. From what I've read network DVRs are not as responsive/quick because of buffering. I seem to recall reading this was a minor annoyance with network DVRs. Maybe it's something I could get use to, but I think manual commercial break skipping will always be quicker via local storage vs network storage.
So like you I want someone to come out with a USB + DVR app as an alternative to network DVRs. It would also be neat if this solution could also double as a network DVR which could stream its stored content to other Android TVs.