I don't have a GHB. Because I work from home, and that's where I am 90% of my life (for better or worse!)

But I would think good things to have would be:

• A street map - useful if you're driving or walking from an unfamiliar location
• Spare cellphone battery
• A pair of walking shoes and appropriate socks, if your normal shoes/socks are dress items not suitable for a long walk
• Waterproof windbreaker jacket
• Sunglasses
• Sunblock
• Insect repellent
• Snacks, capable of long storage times
• Water
• Handgun (for people that don't already carry one as an EDC item)
• LED low-output-lasts-forever flashlight
• For the ladies, toilet paper and feminine hygiene products
• Whistle, maybe even an FRS radio to go along with it
• List of family/friends contact phone numbers (in case your cellphone address book dies with its battery, and you need to borrow someone else's cellphone)

I've never really thought much about a GHB at all. Maybe I should. Work is not the only place you may have to "get home from", so a GHB might be beneficial even for us home-workers.