The iPhone does have a killer app. Communications. Phone, texting. All the rest is 'bonus' but the phone/communication device is a 'necessity' for most. People need a phone for basic life needs. Everything on top of that is bonus, but the killer app is that.
However...
The iPad has no killer app. Its killer app is "lifestyle". Many people enjoy lounging around with it. It's a lazy device for most. A toilet companion. A couch companion. Read some social media on it. Watch some videos. No 'need' but it's a lifestyle enhancer. A lot of you tech guys dont get that grandma/grandpa do not give a damn about the mac or any 'real' productivity/work apps, they read emails, text, etc., and for a lot of the public, the iPad succeeds because it's a lifestyle device.
My guess is the AVP may have a killer app in augmenting your environment. But even if that doesnt pan out, it may do well just as a lifestyle device.
Also what everyone forgets here, almost all current "killer apps" run everywhere. Run it on the iPhone, iPad, mac, PC, Web, android, game console, tv box, toaster fridge. At this point most of the killer apps are available basically everywhere, and your 'style of access device' is also more of a lifestyle choice in how you engage with many portable 'killer apps' than a necessity. Killer apps were needed a long time ago to justify a platform, now all platforms have the same apps, so most platforms do not need any new specific-to-the-platform 'killer app'.
TLDR the killer app is now outdated concept.