No, marijuana didn't just get legalised in the UK without you realising it.
But with the drug gaining legalisation in several US states, tech types have come to the aid of those smokers who might be at a loss to just how stoned they are.
My Canary is a "personal mental and physical performance tracker", telling you how 'with it' you are after taking "alcohol, medication, fatigue or other causes" - so it's still got some use for the UK.
The app's four tests were developed with NASA astronauts and professional athletes, assessing performance on job-related tasks through simple exercises that can be carried out with an iPhone.
The first is a memory assessment, that sees numbers swirl around a screen. Assuming they don't make you throw up, you'll be asked to recall the numbers and their order after a few seconds of swirling.
A balance test works in much the same way as the line-walking exercise police will use in sobriety tests: by holding the phone to your chest and gazing at the ground immediately in front of you, you're asked to walk in a straight line. If the phone detects too much of a wobble in your strides (you'll have carried out the test while sober before hand, to provide a 'normal' level of wobble), it'll notify you.
Other tests include one for attention, as you have to identify a symbol amongst a series of randomly flashing shapes, and a hard-as-nails counting task that asks you to count aloud for 20 seconds, before comparing your attempt to an actual 20 second timer (we'd fail that when totally sober).
The app's developers are at pains to emphasise that My Canary can't "predict an individual's ability to drive or engage in activities that may cause harm or death to themselves or others" - but it's more accurate than turning to your mates and asking if you look alright to cycle home. You can find the app here.
And - all jokes aside - never drink alcohol or smoke cannabis and drive.