Came back to reply to this. I used a Samsung Galaxy S3 smartphone, rigged as I described, in place of an Earl at Elk Camp this year and it worked great. When I was still / stand hunting and settling down at night I used it for reading via the Kindle App, I also used it for land navigation while stalk hunting / beating the brush and riding the ATV to / from Camp. Even while it was being generally abused via rain, snow, and vibration it worked fine.
With airplane mode and power saving mode enabled it went at least three days before it needed recharged. I could recharge from my ATV when necessary but if that doesn't do it then it would be simple enough to grab a $20 power tank that would recharge it twice more give you around 9 days of service. Not too many folks need 9+ days out of their device.
It should be noted that I was in an area with NO (as in zero) cell service so it wasn't being used as a phone at all. Just GPS land navigation, e-book reading, and some pre-loaded mp3s and youtube videos.
Is it as good as the Early could be? No, probably not. Was it good enough? Absolutely.
If the Earl takes another year to launch it'll be a dead device. It's arguably already been caught by generalized tech and in 12 more months it will be SURPASSED by generalized tech.
P.S. Oh, and you'd be amazed at the battery life on your N7 once you disconnect it from the Internet by turning off it's WiFi.