We’re the humans of two cats. One, particularly, is always in great anticipation of our return home, after a day, or sometimes several days, out. For a cat, that’s perhaps a bit exceptional, but, for dogs, this appears to be the rule, not the exception.
LED lights that can be set to millions of colors, and can be configured remotely using your phone, are common and cheap.
So, throwing some code together yourself, or using a service like IFTTT, you could trigger the color of your lightbulb, based on the time required for you to arrive home after a day’s work, the latter pulled from a service like Apple Maps, or any other mapping service that allows you to communicate expected travel time.
Meaning, say, that your lightbulb cycles from red, through orange, to green, depending on how long it takes before you’re home. If dark red, two hours, orange, one hour, and the shades of green, for less than an hour, until it’s a bright green, when you’re about to arrive.
This way, your pet, which, at home, is able to observe the color of the bulb, can quickly learn that the color of the bulb is a strong and direct indicator for the time required until you return home.