To be most useful we'd want minimal manual input from the user during the actual night out - I have a hard enough time logging my taken medications on Medisafe, and it could be risky expecting an intoxicated user to remember if they already clicked a button to mark a drink as taken or not, potentially clicking it twice or not at all and forgetting if they were supposed to click before or after a drink, or they might bump the button while holding their drink and socialising. Hence tracking the drink consumption without assistance would be ideal. I think expecting an inebriated person to be making any calculations would run contrary to the design purpose and also the user profile, which would specifically be people who like drinking and don't like keeping track of drinks when out to have a fun time or people who fear they can't remember how much they have had while intoxicated and can’t be sure of the effects on them.
It would also be ideal to have a way to identify and distinguish different types of drinks and their alcohol potency (basically hardware that can scan the drink).
It would then can then search some central database (or the internet in general) to identify your drink based on ingredients).
In this way it would not rely on the drinker to be cognisant of the different types of drink they are consuming but could make its own calculations.
As extra features, since we'd have this scanning and searching ability, this could potentially also detect date rape drugs and sound an alarm (with haptic feedback and warning lights if in loud bar environments) if your drink has been compromised.
The technology for tracking and alerting you of your drink consumption exists in the form of a smart water bottle for tracking your hydration needs and water consumption
, using very sensitive sensors at the base which can even tell the difference between your drinking vs spilling water.
This existing design could be adapted to a glass (probably easiest to start design on some kind of tumbler, although it could also come in wineglass varieties, with the sensor then likely embedded in the bowl of the glass itself rather than the stem or base, for accuracy of consumption tracking and easier drink scanning).
Perhaps when you have had enough it could give haptic feedback or flash an unobtrusive red, amber or green light on the glass depending on if you have had too much. Your body mass and other factors could have been configured via a syncing app beforehand.
Another benefit of this scanning and utilisation of an app could be the ability to also have this sync with your medication-tracking and apps tell you if any medication you have taken recently or chronic medication you are on could contra-indicate with what you are drinking, as is frequently a concern with alcohol.
It would be ideal if the glass itself was sturdily built but also collapsible or compressible, particularly as it is being transported potentially in a handbag or pocket, so traditional glass as a material would be out due to it being dangerous, but building collapsible glasses in a hardy material (possibly gorilla glass if one is not a fan of plastic?) or even foldable silicon could make it easily and safely transportable, and being translucent, could also make it easier to hide the tech itself if that is desired, although making it a visible feature could still be done stylishly.
Some limitations are that it currently cannot take very hot or cold liquids, so ice would be a problem, especially if the ice is put in first.
Potentially it could even sync with the app to track your historical consumption and give you insights as to your drinking patterns when you are sober, so you could better plan your budget for an evening out, or identify whether you have a drinking problem.
If we want the app to be more interactive and not only for preconfiguring, it could also give you on-screen information about the drink in your glass once identified and potential advice, to help you be informed on your consumption in the moment, so that you can consciously slow down when you're confronted with the actual potency and potential effects of your drink on screen. Warnings could also be displayed if previous drinks could also interfere.
Ideally, this app could also integrate with other apps such as your location, to pop up remind you that you are not in a safe condition to drive and to order a cab before your battery gets low, potentially integrating with apps like Uber, to also reduce the risk of your being tempted to get a lift with a drunk driver.
Very often the biggest affector of people getting drunk is the shots they take in between drinks, thus the ability to track shots would be essential for many people.
Having a spare glass, or actual smart shot glass would be advised if you are partial to shots, as your main glass would likely be occupied by a drink since shot-buyers seldom wait for you to finish your main drink before buying a round of shots.
Designing a smart shot glass might be harder to do due to size constraints for the hardware, also harder for a drunk person to keep track of which one is theirs unless it is a different colour (which may make it a target for stealing since many people seem to steal novelty glasses from bars).
Also the custom of slamming a shot glass down on the table after knocking back a drink would likely damage the sensitive sensors at the base unless there's some specially designed cushioning there.
On the other hand, we would likely not run the risk of people putting ice into a shot glass (though icy cold drinks may still be a risk) so we could possibly trade off temperature protection for protective cushioning at the base in terms of space constraints of the tech.
Or possibly you just carry around a spare smart tumbler, and when someone buys you a shot, do the slightly uncool thing of transferring it to your tumbler - something best done while wearing an old cloak and cosplaying as Mad-eye Moody while eyeing people around you suspiciously. 😉