I, too, have a propane fire pit for burn bans; it is much too big for in-tent use but works fine just outside the awning, when we are grouped outside.
Tank heaters like the one pictured in the first post work ok but like buddy heaters and most other non-thermostatically controlled heaters they use excessive amounts of propane.
For a while I tried using thermostatically controlled "Blu-flame" heaters. They reduced the propane usage but caused condensation on the inside of the tent (first and only time that I ever had condensation issues). They also had similar altitude issues to the buddy heaters with respect to the oxygen sensor (some (most?) work at altitude some don't).
I have tried most types of tent theaters, including Coleman lanterns and oil heaters along with several types of military heaters and wood stoves so far no Joy... excessive fuel consumption, poor heat control, require excessive attention, extra fuel types, too many fumes or are too big bulky, messy etc. etc.
The heaters that move the combustion outside the tent and duct the heat into the tent look like the best, and most expensive, bet so far.
I have also tried liquid alcohol fireplaces, and gelled fake fireplace fuel; besides requiring another fuel and the open flame, their heat output decreases at altitude making them less than a good choice.
Now, if I bring a heater at all, it is only used to preheat the tent before going to bed or getting up... a decent sleeping bag takes care of the rest.
Enjoy!