Are any of those examples really only convincing if they can vibrate the phone? Surely a scam that just involved that fake call screen while playing a fake ringtone would be more or less just as effective? I can't imagine it's a lot of people who wouldn't be fooled because they think "oh, it's fake, it's not vibrating" who would suddenly be fooled by this.
I think the percentage of people browsing the Web while not looking at their phone is pretty low. I'm also not sure how the vibration would convince people who don't know how to use their phone. I would suspect this group would require less effort to manipulate.
My point was that I don't think the vibration would make much of a difference. But you're right that a small gain in the effectiveness could be worthwhile.
How many people only have their phones on vibrate and are used to feeling a phone call come in versus hearing/seeing it? Many professional workers would have their phones set up this way. A sudden absence of vibration would just feel weird.
