I think we need to be careful of adding "more technology" to solve a "problem", when the current technology should have prevented it, but other (Human) factors prevented it.
The "Human Factors" here were poor worldwide management in ensuring that all Flt Crew and Manuals were at one over obeying the RA rather than ATC. That was quickly corrected... so the problem should not recur. (NB of course TCAS works perfectly well if one aircraft ignores the RA).
As has also been stated, the RA is a last resort. Why did we get to the last resort? Again, Human failings - largely Management again with the staffing levels and disabled technology at ATC. All this combined with one small error and the tragic results.
Let's concentrate on correcting the identified error's (largely done?), rather than inventing more technology to cope if this particular set of c*ck-ups occurred again.
NoD