Do you have a Pebble in the UK? You can use a custom watchface to turn it into a Tesco clubcard!
After reading this post on Reddit about adding a Starbucks barcode to a Pebble, I was inspired to try it in Tesco. The process (described in detail in the post above) involves first creating an image file of the required barcode, then using an online watch face generator to generate a watch face from the image which is then deployed to the Pebble via your phone. There's a couple of differences between the Starbucks card and a Clubcard - primarily the barcode is much longer, which made me doubt whether it'd work.
Sure enough, on my first test, it didn't want to play. I had used a black background which I figured was a mistake and next used a white background. It took a couple of tries... but (at a self checkout) - success! I think if I make the barcode fill the watch screen better it will be even more reliable! :)
There's 2 things I had to do over and above the tutorial linked above to get it working - I used the CODE_128 barcode type (required for the clubcard number) and I DIDN'T use the number printed on my clubcard. Why? Simply because when I scanned it with the Barcode Scanner app, it reported a different number. I used that one. :)
It's pretty neat really. I need to try it at more scanners now (a regular checkout and a petrol pump for example), but i'm impressed. :)