Regardless of what I said about Shazam on the Apple Watch, there may not be a "killer app" for the wearable platform yet. But if you take Shazam, some of the health apps, fun apps like Swarm for Watch and the new QuickPark for iPhone and Apple Watch (free) and lump 'em all together, you have a bunch of apps that make the "need" for an Apple Watch very compelling.
QuickPark does two things very well: it remembers where you parked your car and it reminds you of when your parking meter (if you're parked at one) is expiring. Between those two functions, you should keep yourself from walking around in circles trying to remember where the heck the car is and getting parking tickets when you show up at the car just after the meter attendant slips a ticket onto your windshield.
QuickPark works similarly on both iPhone and Apple Watch, but to me it's much more useful as a Watch app so that's what I'm focusing on here. After installing QuickPark on your iPhone, it appears as an app with a simple blue icon sporting a "P" similar to a parking sign. It can also be installed as a Glance.
To demonstrate how QuickPark works, let's imagine a quick scenario. I drive to a location and find a parking spot with a meter. Just after I've paid the meter, I lift my Watch up and tap on the QuickPark app icon. I'm greeted with the simple interface with two commands seen at the top of this post: Park my car and Find my car. For the sake of the example, I tap on Park my car.
The app shows me the time when I parked, and the iPhone app is busy capturing the location of my car. With a swipe to the left, I can enter the amount of time I purchased on the meter in hours and minutes -- entry is done with a tap on the appropriate time field, then using the Digital Crown to dial in the correct number. Swipe again, and QuickPark asks if you parked in a structure where you might have difficulties finding your vehicle. If so, or if you just need to remind yourself of something, a tap on the microphone icon lets you record a quick voice note -- for example, "I'm at the meter on Wazee Street across from the construction site."
Swipe once more, and you're done entering the critical information. With a tap on the Finish button you're back to the QuickPark screen.
Later, QuickPark reminds you when you are getting close to running out of time on the parking meter. Tapping on the app icon, QuickPark displays the remaining time, a map of the area that can be tapped for walking instructions to the vehicle, and a button for playing back the voice note you recorded.
QuickPark represents what I love about well-implemented Watch apps -- it performs a task very well (marking the time and place of parking your car, reminds you when a meter is getting near running out, and then gives you directions to the parking spot), it has a clean interface that makes immediate sense, and it's right at your fingertips all the time.
Anyone who parks a car in a crowded, confusing metropolitan area needs QuickPark, and at the price of "free", there's no reason to hesitate in installing it on your iPhone and Watch.