"Gun Locker" sounds like a great place to pick up a firearm for free when it gets dark. Enterprising young fools will see it as a hunting ground. After all, youth doesn't assess risk well, and a free gun plus street cred getting it is one way to impress those in the 'hood.
Just pointing out one unintended consequence.
I had the same thought years ago when I heard about delivery lockboxes that attempted to conceal the identity and contents of things shipped to them. Decided that daily warrants and a Bomb Squad truck would likely color the nature of what I would be trying to market in the way of secure storage.
This hypothetical scenario is simply assigning a name to the owner of the property. In most cases, the exact same conditions exist for everyone working for somebody other than themself. It's a bit inaccurate to generalize, but all commercial property used for manufacture, storage, and sale of goods in America is posted off limits for guns. Even the store clerks working behind gun cabinets in Walmart and Academy can't carry. We aren't alone, I speculate the majority of us are subject to the exact same conditions. MOST of us are working on somebody else's property - their house, their rules. The majority of Americans can't carry at work, and company policy prohibits having guns on the property even if stored locked in the trunk of the car, in spite of state law.
It's the real disarming of America, at the corporate level.
If you do choose to store a firearm in the car, do so carefully, and be careful how you access it and where. Getting it out of the trunk, openly displaying it as you put it on, etc., is exactly how people get fired. Having it openly seen in a door panel pocket for other coworkers to view is another - had a customer just yesterday with a nice compact 1911 visible that way.
As for getting it stolen, it goes to what kind of car you drive and why thieves would be attracted to it. They steal nice stuff from nice cars, i.e., if you presume to flaunt a high dollar lifestyle in your choice of vehicle, expect them to steal from you. Leave an Iphone 5 laying on the seat next to a loaded magazine, or empty cartridge boxes thrown in the back seat, along with a high end stereo and a huge sub woofer visible, you are advertising. While we may defend the right of a 16 year old to dress like a hooker and walk in dangerous neighborhoods, claiming you can do the same with your car isn't realistic.
As said, muggings and carjacking are known to happen. Conduct yourself with a mind to minimizing it - survey who is getting mugged and what kind of car is jacked, and make appropriate decisions.