I've just read a interesting article – 'Mapping Out The Future With TARDIS' in the journal Jane's International Defence Review (Volume 39, November 2006, page 29 Upgrade Update). Despite the title, this isn't about The Tardis (wikipedia) time machine featured in the Doctor Who sci-fi television programme; but instead the Tornado Advanced Radar Display Information System developed by BAE Systems for the UK Royal Air Force's Tornado GR-4 ground attack aircraft.
The Jane's IDR article discusses the Device Software Optimisation (DSO) strategy adopted by BAE Systems, and a high-level overview of TARDIS' capabilities. TARDIS actually uses state-of-the-art active matrix liquid crystal displays can be used by the Tornado pilot and navigator either co-operatively or
independently, and perform data fusion of radar data and digital
moving map display data to provide advanced enhanced situational
awareness for low-level terrain navigation and avoidance capabilities.
TARDIS performs data fusion and display by using a high-performance multiprocessor architecture, with interprocessor communication via VMEbus backplane. Monitoring communications between multiple processors in a real-time system can be challenging, especially when using an intrusive development tool such as a debugger which can affect the real-time timings, but BAE Systems' engineers were able to use the Wind River System Viewer during the system integration to observe the real-time performance of the TARDIS subsystems. You can read about this in more detail in the case study (PDF) on the A&D Customers page.
So, to a certain extent TARDIS does behave as a time machine, enabling the RAF pilot to navigate forwards in time and space..but not backwards in time as this would violate the Hawking Chronology Protection Conjecture (wikipedia).