The Maillard reaction begins around 150° C. You do not need that exact temperature. Usually, you don't even want that exact temperature; even baking temperatures usually hover around 175-200° C (350-400° F), and those temperatures are held for 20 minutes or more. Pan-frying is almost always a fast cooking process lasting no longer than 10 minutes.
Thus, almost every cooking oil has a smoke point at or around the ideal temperature. Butter is a bit too low around 121-149° C (250-300° F), but the vast majority of liquid oils - peanut, sunflower, corn, canola, sesame, even EVOO - all have smoke points from 150-260° C (300-500° F).
See Wikipedia's list of smoke points for a fairly complete list. Avoid butter and unrefined flaxseed/safflower/sunflower oil (commercially-bottled oil is almost always refined, except for EVOO).
Of course, this doesn't say anything about cooking time or sticking. When we talk about frying or sautéing in oil (i.e. to get the Maillard reaction going), we usually want a quick sear, and for that you really want to get the pan screaming hot so that you can get a good sear on the outside without doing much to the inside. Clarified butter, coconut oil, or any other of the highly-refined oils are the best for that purpose.
If you're really trying to prolong the cooking time, i.e. pan-frying a chicken breast all the way through, then I guess you'd stick with a lower smoke point oil, such as EVOO or unrefined peanut or sesame.
We use kosher salt to clean (still-warm) cast-iron by pouring in a handful then rubbing around with a (usually paper) towel. The kosher salt grain size is just right to be an abrasive for removing excess grease and other food particles, and you don't have to worry about it melting. Then a wash with hot water and a little soap to complete the washing, followed by a rinse. To avoid rust, we dry the pan by putting it on the stove, high flame, until the water has evaporated.
We have to re-season the pan every once in a while (once or twice a year), but this method has worked well for us.
Best Answer
Sauté / stir fry : When you're just below the smoke point of an oil, it'll shimmer ... but that's only useful for a precise temperature if you know what the smoke point for that oil is, and you actually want to use oil for cooking.
Grilling : I can't remember if it was an episode of Good Eats or on Alton Brown's first book that he recommended that if you had an automatic ice maker, so had consistent sized ice cubes, that you time how long it takes them to melt at different temperatures, so you could use that to judge how hot a grill is.
Grilling / Pans in general : For grilling, and campfire cooking, I've always gone with the hand near the cooking surface to gauge how hot it is, but I don't know that it's all that accurate ... and people have a different tolerance for pain, so you'd have to do some tests to calibrate. It doesn't work as well for cooking on a stove except for cast iron; I suspect it requires a more radiant heat source.
Deep / shallow frying : I like the wooden spoon test -- dip something wooden into the hot oil, and as there's moisture in the wood, you should see small bubbles rapidly form if it's hot enough.
Searing : Listen as you add food ... After you've added a bit of oil, touch the food to the pan, and you should hear sizzling. If it doesn't, pull it back and wait a few more minutes for it to heat.
Breadmaking : If I need warm water for making bread, I'll run the hot tap against the inside of my wrist ... once it feels slightly warm, but not hot, it's just above body temperature, so should be good (around 38-40°C / 100-105°F)
None of these are going to be completely precise, but there's lots of ways to gauge temperature other than a thermometer.