The problem with gadgets in general is that at first may seem a good idea but end up complicating things or being a crutch.
The best location for an alternate is on a bungee around your neck. You can get to it without using your hands and it’s always there. You donate the reg you were breathing from which is on a long hose. In a real emergency (i.e not the happy smiling divers kneeling on a platform and exchanging big signals "we have all the time in the world") an out of air diver will RIP the regulator out of your mouth. So better be ready, tuck your chin and get to your backup.
No need to have a 7’, a 5’ is sufficient for a rec divers/no pen dives. The only reason it is not thought at the recreational level is because of fear of task loading beginners. Unfortunately in the advanced courses it’s not brought up (mainly because instructors are unaware/unwilling to learn themselves).
Another good one for the useless list: the rubber necklace to hold the alternate around your neck, really easy to pop out, completely defeats the purpose.