A number of smart people have suggested that hyperinflation is the inevitable outcome when the debts of the nation are monetized on a regular basis. How can we measure this?
Economic historian Peter Bernholz wrote a book analyzing hyperinflationary outcomes, and came to the conclusion that hyperinflation is inevitable once the central bank monetizes 40% of total government expenditures, while at the same time consumer sentiment is high and/or increasing. Here's an article dated Dec 2009 by him saying "it likely won't happen here." That's reassuring, but it is based on what he saw at that time. Currently the Fed is engaged in Open-Ended QE until 6.5% unemployment is reached (aka QE Forever, QE to Infinity, the beatings will continue until morale improves, etc) and so it seems like a good idea to monitor the monetization realtime. However, data series for measuring government spending come out with a 3 month time lag, so its not exactly realtime.
Money velocity is another sign of hyperinflation, as is falling exchange rates. When people are afraid to hold the currency of the nation, that by itself can bring about a hyperinflationary situation. Money velocity updates quarterly, however exchanges rates update weekly.
Bond yields used to be a good "canary in the coal mine" for inflation. Specifically, "inflation-protected" bonds would see their yields jump as soon as inflation was detected by the market. However with the Fed buying these bonds, the canary has been effectively muzzled.
In addition, currency reserves held by central banks around the world report their holdings to the IMF every quarter. Currently the USD comprises about 60% of allocated central bank reserves. If that were to decrease significantly, that would directly impact the US treasury market, since central banks hold currency in the form of sovereign debt, likely putting pressure on the Fed to increase monetization.