Invisibility Cloak, etc.

http://www.howstuffworks.com/invisibility-cloak.htm
Fascinating technology that's finally becoming less classified.
http://www.unknowncountry.com/news/invisibility-cloaks-are-now-science-fact
However, much of the general public still might be too busy or simply don't care about such technology & its implications.
http://www.independent.co.uk/life-style/gadgets-and-tech/news/new-active-invisibility-cloak-design-drastically-reduces-visibility-8934474.html

While invisibility technology is possible, time travel technology remains officially theoretical.

"The Doctor without his time-travelling police box is difficult to imagine, but its creators initially proposed he journey through space in an invisible machine covered in light-resistant paint."

http://news.bbc.co.uk/2/hi/uk_news/magazine/7736130.stm

The Doctor's TARDIS - Tardis Data Core, the Doctor Who Wiki

tardis.wikia.com/wiki/The_Doctor's_TARDIS‎

You may be looking for the Doctor's first TARDIS. ... (AUDIO: Quinnis) The Fourth Doctor showed Adric how the TARDIS could be changed to the ...... the ship's visual stabiliser, causing it to become invisible when it materialised again on Earth.

http://www.thedoctorwhosite.co.uk/tardis/interior

Quite a fascinating 1960s TV series depicting a time traveling spaceship that's much larger on the inside.
http://tardis.wikia.com/wiki/Chameleon_circuit

http://www.dailymail.co.uk/sciencetech/article-2394412/The-Doctor-landed-Google-Street-View-places-TARDIS-outside-Earls-Court-Underground-station--peek-inside.html