Like Todd said. A small MAPP torch might be JUST enough for 1/2" rebar but it would take a long time to heat up and in fact might not work very well at all. So acetylene is your best option. Pretty much the only efficient option unless you have access to a portable gas/coal blacksmith forge.

The way I'd do it: clamp one end in a big, heavy, securely mounted vice. Mark the rebar with chalk or file a notch in the middle. Heat the spot until red hot at least, preferably bright yellow, then bend around something round and made of steel. If you need a sharp bend, heat only a localized spot. For a gentler curve heat a longer length.

That said, if you need more than one element you'll probably need a jig to ensure a consistent bend. You COULD do it by eye & hand but it takes practice and some skill to do it right.