What kind of flight termination measures are taken for supersonic aircraft?
Aircraft like the B-58 and XB-70 Valkyrie were equipped with escape pods to aid in super sonic ejection. The pod its self came down around the seat when activated the only movement that appears to have been required was bringing you legs up a bit. Heres some video of the capsule in testing.



(source)

You can find some more info on the only XB-70 capsule ejection in the answer here. There is also some interesting info on the topic in this Physics.SE answer.

Ultimately getting lower and slower may be your only option as was the case during an SR-71 ejection.


  Since the chances to survive an ejection at Mach 3.18 and 78,000 feet
  weren’t very good, Weaver and Zwayer decided to stay with the aircraft
  to restore control until they reached a lower speed and altitude, but
  the cumulative effects of system malfunctions exceeded flight control
  authority. Everything seemed to unfold in slow motion, even if the
  time from event onset to catastrophic departure from controlled flight
  was only two to three seconds.
  
  It was at that point that the pressure suit proved to be very effective protection for Weaver. In fact, once it was inflated, an emergency oxygen cylinder in the seat kit attached to the parachute harness was functioning. It not only supplied breathing oxygen, but also pressurized the suit, preventing Weaver’s blood from boiling at the extremely high altitude. In this way the suit’s pressurization had also provided physical protection from intense buffeting and g-forces. That inflated suit had become like a tiny escape capsule.


There is some interesting footage of wind blast testing on flight gear and seats for the F-106 aircraft you can find here. According to some of this data the helmet and flight suits were capable of surviving wind forces in and around Mach 1.3 and the seat was capable of ejecting at those speeds. However in the case of the F-106 line of aircraft it was ultimately deemed that 0-0 ejections were more likely (and a higher priority) than high altitude high speed ejections. Since no seats were capable of both ejections the 0-0 seats were ultimately favored. (check out this for more info)