Since posting http://verahill.blogspot.com.au/2013/08/498-briefly-drawing-nmr-pulse-sequences.html I've had a look at this: http://www.celos.net/comp/pulses/
And that actually is (almost -- let's not get carried away here) exactly what I have been looking for. The main issue was that it's meant for metapost -- or rather, the main issue was my unfamiliarity with metapost. Anyway, my life is know complete.
So here's how to get started...
First 'install' the metapost script:
sudo apt-get install texlive-metapost mkdir ~/texmf/metapost cd ~/texmf/metapost -p wget http://www.celos.net/comp/pulses/pulses.mp sudo texhash
Next, time to test-drive it
mkdir ~/tmp/pulse_test -p cd ~/tmp/pulse_test vim test.mpinput pulses.mp beginfig(0); initf; startline(rf,"RF"); xline(1); xpulse(0.5,0.5,"90"); ospan(-0.25,-1.0,1.5,"d1"); xline(0.75); xpulse(1.0,0.5,"180"); ospan(-0.5,-1.0,1.5,"d1"); xline(1.0); ospan(0,-1.0,1.5,"vd"); xline(1.5); xacq(2); endfig;mpost test.mp mptopdf test.0 pdftops -eps test-0.pdf test-0.eps
Now, I somehow suspect you can embed metapost scripts directly in .tex documents, but from my brief testing I haven't quite managed to make it work.