Anything that would maybe get conviction rapes up is a good idea
However I can already see the defenses for it and the accusations of lying still. All it would be would be the likes of 'we were roleplaying'. Etc. There will always be a lie. And it will be accepted near every time too. Many people freeze when raped/attacked and the ability to speak is gone totally (apparently the majority mammal reaction) so even if they could move to get the alarm thing, it would just be the sounds of one person having sex (or more if mutiple attackers) and it could be claimed that the victim just did not make a sound during a consensual encounter. Or sometimes, the sounds made when in pain/trying to get away sound fairly similar to those in pleasure too
Edit. Though connecting automatically to the local police station (and the police to actually respond) could be a good help actually, if such a device could be made. Could help in many cases too, the likes of 'normal' assaults, muggings maybe, an such.
What
would help, would be to stop allowing defence teams to bring in irrelevant stuff such as the victims previous sexual history, when the victims team is not allowed to bring up anything about the accused life, even the fact that they have previous convictions for rape! Its just disgusting that this girl spent 8 days being cross examined where the actual accused people got a few hours. Who exactly was on trial here?
Also I think in sexual assault cases (and possibly all serious cases tbh) a panel of experts should be used rather than a jury. Tbh rape myths are far too widespread and repeated in the media and such on a regular basis and so many people believe them so its never going to be a fair trial. If a person does not act like 'the perfect victim' (ie. crying nonestop for a week afterwards, developing anxiety, etc) then they are automatically lying to many people.