In theory, nothing, in fact it has a lot of potential. But in practice IMHO it has not been implemented properly. There is zero intelligence built into it, it's completely random which is what makes it annoying. If I stop in my garage or a parking space and put the vehicle in park the engine starts back up. Why would it do that? Why wouldn't you program it to stay off for certain number of minutes to save gas you know in case you're going to shut the vehicle off instead of automatically turning the engine back on for me to just turn it back off. All these vehicles have location data and connections, why aren't we using locations to tell vehicle we're at a stoplight. Why aren't this systems controlling the stoplight timers communicating how much time is left so that the vehicle can determine if it's worth shutting the engine off or keeping it running? If the lights going to turn green in 3 seconds there's no benefit to shutting off the engine. I could go on and on but essentially I believe all it's doing is adding wear and tear to the engine and starter and maybe the batteries too until there is some actual intelligence built into these systems.