Re: emergency transporter armbands
The device Data had could be nothing other than a portable entirely self-contained transporter unit, and not just mearly a remote control because the transporters on Enterprise were offline. That's why he jumped over in the first place.
Still a stupid device. The only reason this device existed in this movie is because 1) Data had to die, and 2) they had already used the "I can only bring you back one at a time" method of leaving someone behind in the franchise.
"You have been examined. Your ship must be destroyed. We make assumption you have a deity, or deities, or some such beliefs which comfort you. We therefore grant you ten Earth time periods known as minutes to make preparations."