Except that I think they are hosting their own DNS... I'm not able to retrieve their SOA information even at the moment.

ouch. been awhile since i've seen that failure mode.

Better still cloudflare-status.com or similar: separate domain, separate registrar, separate DNS, separate hosting.

Or just use twitter :)

I wish there were a business model for a third party site-monitor and site-uptime service, which let the site owner do more than just post updates, but also prevented the site owner from lying about historical data.

Basically New Relic (that actually worked) + Pingdom + Internet Archive + Twitter + status.example.com.

Pingdom allows you to embed (JavaScript, IIRC) data on your own site showing your status/downtime/etc. from their perspective.

true, but let's add to the criteria:

reliable, accurate, high-frequency

Yeah, but then what if that site went down? :P

Doesn't really matter -- as long as the odds outages at both sites are independent, and relatively low, it won't happen at both at the same time, usually. You can make the status service pretty reliable, cheaply, compared to most other services, and if it loses the central servers, the remote monitoring nodes can still store test information, so when the service comes back up, the historical record should be accurate.