Megasquirt is okay, as far as it goes! (it is not a stand-alone bit of kit).
It controlls the injection, but to get the ignition timing you also need the 'Megajolt' unit.
It has got a few limitations, but is programable in 3 dimensions (it may be 3 by now, it was being developed last time i was looking into it!).
The big advantage is that it is home buildable either from a kit, or just a pile of components.
I run the megajolt on the Dolomite to map the ignition, but it is still on carbs so only maps in 2 dimensions.
Its other limitation is that the 'steps' where ignition advance is changed are quite wide by comparison to other units.
It is brilliant for use on any car with a standard distributer ignition, but maybe not as advanced as a decent ECU.
The whole system was originally designed by a guy called Brent Picasso (not the artist

) and has been developed by anyone who can offer an improvement! (A bit like the LINUX alternative to Windows).
For further info, have a look
here