i am only still hearing is a gg with a headphone jack,
since i dont think androids can connect to mulitple usb simultaneously yet, you really need a all in one device, plus what kinda interface? ie what kind of resolution on screen, touchscreen? how advanced is device?
This is a huge project you are taking on, and may take a long time if doing by self.
Instincts recommend you breaking it down a bit, ie
1) design your collar with standard headphone/mic jack, if it doesnt already exist, email samsung to put jack in gg (thats a guesstimate timeframe for both completeions), all i can think is that if you want both colar and screen to be on bluetooth , you will need your designed device with two radios or alike.... I think i read that gg is android os, so that means you can learn droid code for it and make your own apps , while you wait for them to come out with headphone jack
2) also what is the complexity for your screen buttons, regardless, doing your own circuits will mean your own code , plus code on phone to interface with your devices,
3) simply reinventing a BT headset with few extra buttons maybe more feasible for you , but that means cutting out the display, and
you will still need to learn coding, for device, and again maybe for phone depending on complexity
overall i hafta say that if you are on your own with this professionally you will need to throw $$ at it and hire a team. doing self you wont stay ahead of market.
if this is hobby then start with code, by learning how to program phones, you learn how bluetooth and stack/firmware operate and communicate, same with display you choose
from there you have chance of learing cpu power to design with all your peripherals and their limitations/requirements, and then you can do schematics, so you can choose what arrangement is to your liking, this is a new device so nothing will exist, you will need to think it from ground up, for example lets start with identifying what textile control panel and screen you would like to use for your design, rsvp with link
**broken link removed**
--- getting one of these comes with voice command, you may get what your lookin for? again may need extra phone code to do more!