By popular, I just meant off-the-shelf SMD LEDs.
Again it doesn't cut it. Their are lots of different off the shelf SMD LEDs. They all have different sizes.
See the different types here http://uk.farnell.com/w/c/optoelectronics-displays/led-products/prl/results?st=SMD+LED
on something like a Ruuvi
What is a Ruuvi? Links are needed if you referrer to anything obscure.
re-purpose it as a BLE sensor
Again what are you talking about? You know but please be aware that not everybody knows every obscure commercial trade name.