Hi. i'm planning to use Vuforia as the AR engine and google cloud recognition for voice. You should know that this services are almost ready-to-use but are services that may incur in costs in the future. So it is important to stablish your goal for this project: if this app is a prototype it's fine and you may get it to work for many users for as low as cents, but if you're planning to release it on a store, then you should take into consideration the license for Vuforia and the computing costs of google cloud.
Anyway, I can do this app for you, no problem. Just give me the details and I can start to work on it.
I'm an expert Unity develper, specialized in VR/AR. I've led development for the last years in the company I cofounded. We currently have an AR app for Museums running on two countries, so sure I can help you with what you need. I'm brand new on freelancer but I work hard and neat so we'll be just fine working together :)
Feel free to take a look at my profile.