Paul Wilson: on the 757/767 and most other large a/c each tire has its own pressure guauge built into the tyre/wheel assembly that gives the current pressure and Mr. Boeing kindly writes the required pressure some where on the gear struts.
Some aircraft have a onboard pressure indcation system but is usually only offered as a rather expensive customer specific add on - perhaps for larger types destined for short turnarounds I.e. the 747-400D.
As for flat tyres or the more exciting burst tyre on take off: Various advice is given from training manuals but they all state the same thing, don't reject the take off for one and on the 757/767 a single tyre lossed on a main bogey is a deemed a relative non-event when it comes to landing. Runway length permitting.