Keep a crossword puzzle (or another fun book) in the glove box of your car! My husband and I go for little drives in the car and sometimes he'll stop someplace to pay a bill or whatever. We don't always want to lug the baby carrier in and out so I stay in the car with the baby, and I'll pull out the puzzle book and keep myself occupied for the few minutes he is gone!
Source: I was sick of waiting for him in the car and just decided on this, it works!