Dunno about the 777 but our new shiny 757-300's have a tail skid which when hit, causes a few sparks. If the strike is severe, the sensor which looks like an antenna behind it scrapes, opening the circuit through it giving EICAS msg.
The tail skid has a crushable can inside it and the tell-tail markings should be visible on a walk round.
The -300 looks chuffin long compared to the -200! They have reduced the rotation angle to 15deg (instead of 17deg) At that angle there is only 26in clearance to the runway. To try and prevent tailstrikes Mr Boeing has added extra feel so that the stick-to-seat-interfaces don't pull so hard!