The E911 issue might be problematic in the coming months and years as the older networks get shut down and everyone pushes to VoLTE voice service. There's also the issue of callback with E911 and triangulation services. The network technology changes and fragmentation is making the SIM-less 911 emergency phone idea harder and riskier moving forward.
Of course, with Google Voice, as it's free? You're the product being bought and sold. It's also not as reliable and robust as you might need/want. Speaking of privacy and security, I wouldn't be so hot to just randomly connect with every indiscrimiate WiFi hotspot in the world, and would recommend at minimum a VPN service going this route as well, but that's also going to deeply impact call quality with any VoIP solution adding considerable latency. You ultimately get what you pay for. As such, be frugal, not cheap. Your life and your privacy should be worth more than a few shiny baubles. Be willing to pay for what you actually need.
If you want emergency fallback calling service, H2O Wireless is one of the few remaining MVNOs offering PAYGO, and still has it at a reasonable rate. Minimum $10/90 days, 5¢/min/SMS, 10¢/MB/MMS, no monthly connect fees. You'd be looking at $40/year and it'd give you AT&T coverage.
It's also worth noting that RedPocket has annual plans with 100 minutes, 100 SMS and 500MB data a month allotments for $60/year, and they offer service on all four major carriers. Given your average Ting bill, it could likely cover what you already use and then some, assuming you're using the minimal tier across the board. Perhaps instead of going hardcore WiFi only and letting Google datamine you in exchange for dodgy phone service, spend the little extra and just use a lower cost MVNO than Ting.
