Powerloader - Is there any real situation (other than climatic battles with Alien Queens) where this machine would be more effective than a wheeled machine (eg a conventional or all-terrain forklift with specialist attachments)? A ‘loader wouldn't be able to climb anything other than shallow steps and would have too much foot pressure to work on soft/unstable surfaces. Additionally, the Powerloaders in the film move much slower than any forklift.
That's before you think about how you'd actually design the machine. Since it's not inherently stable, the ballast would have to be many times heavier than the maximum weight that the machine could lift. The ballast would also need to be dynamic and moved in someway to make sure that the centre of gravity stayed above the tiny feet.
Since this dynamic ballast has to be moved, it would have to be smaller than the enclosure that it moves in. The Powerloader isn't much of a hunchback, so I can only conclude that it could lift only a small weight (~200kg) unless the ballast is made from some incredibly dense space-age material.
Video Phones - Been there, done that, put one in my pocket. The picture quality of the videophones and the helmet cameras already looks ridiculously poor. Digital video and exotic modulations means that current technology could make helmet cams of excellent quality and total robustness up to their rated maximum range (Spread Spectrum or Ultrawideband etc)
PDTs - Cisco Systems and others make incredible tags that use special corporate wi-fi installations to track equipment and people on large premises like hospitals. Some include biometric transmission and even 2-way voice. The most amazing thing is the size (badge size) and amazing battery life (months).
Remote control dropship - we have fly-by-wire and experimental remote fighter planes. Not much of a leap ...
FTL - Well, most physicists say it's impossible. I like to think they are wrong!
As for the Aliens themselves, I believe that it's perfectly possible that somewhere in the near-infinite Universe, there must be a creature very similar.