I'm not really sure to what you're referring on the second half of your post. Mention is made repeatedly of the fact that data bursts take time to execute, and that most of the information being relayed back and forth is small; tactical positions, status updates, small personal messages, etc. All of these could be done with a single Ad-Hoc wifi connection in our day and age, with our tech.
The power requirements for the brain pal were handled internally by the device itself. In other words, it had a battery. Perhaps one that could be charged off the body's own internal energy sources? Remember, these bodies were basically designed to be the ultimate combat chassis, and so the fact that the body's own internal electrical field could be used to do something like that...not a big deal.
Finally, in The Last Colony, a huge deal is made of the fact that the enemy *can* intercept electronic transmissions, to the point that not a single colonist on the planet is allowed to have a BrainPal active, even the military personnel, unless they're in a specially shielded bunker. In fact, nobody is allowed to have any form of electronic technology that could so much as broadcast a byte of data, because it could be picked up *across the solar system* by an enemy ship.