A couple of minutes work in Excel has produced the following Patent Fly Stimulator Reciprocal Heading Practice Engine!
It requires a massive two cells to work.
It the first, enter this formula:
=ROUND(RAND()*360,0)
In the second, enter this:
=MOD(address of first cell+180,360)
That's it. Every time you press the recalculate key (F9) you'll get a new heading and a new reciprocal.
Obviously this makes the task a trifle easy, so you may wish to cover up the answer cell in some way (scroll it off the screen, set the text colour to the background colour, drag something else over it etc., etc) so that you have the chance to work out your own answer first.