Car ownership is mostly a list of chores. You pay for gas, tires, and oil changes just to keep the thing moving. Adding a remote start is one of the few upgrades that actually makes the car feel better to own. It turns a freezing winter morning into a warm commute without you sitting in a cold cabin.
Most people wait until the first frost to call an installer. By then, shops are booked and prices are firm. If you buy in late summer, you have more leverage to negotiate the labor cost. You can handle the $450 installation by splitting it into small chunks before the cold weather hits.
This isn't free money. The 0% window is a hard deadline. If you still have a balance after 18 months, the standard high interest rate kicks in on whatever is left.