It has become apparent over the course of the pandemic that some patients appear absolutely fine and apparently not in distress but have oxygen levels so low they would normally be unconsciousness or even dead.
We highlighted it because medics raised the alarm that many people were getting to hospital too late and should be brought in much sooner.
NHS England told me exclusively they were looking at changing guidelines for 111 call handlers and they were looking at giving patients devices that could monitor their oxygen levels at home.
For the families of those who have died it was a small victory.
Today the NHS has made good its pledge to look at it.
A pilot is now underway in 11 hospital trusts where some Covid-19 patients and at risk patients are being given oximeters.
Emily Morgan explains how the device works:
These are really simple devices which clip on your finger and give you a quick and easy reading of oxygen levels in your blood.
The results are pinged via an App back to doctors who can keep an eye on them.
It's so simple and so clever that Dr Andy Barlow from Watford General Hospital says it will absolutely save lives.
This device 'has been absolutely crucial':
Why then has it taken this long to launch such a service and why is this just a pilot?
Sir Simon Stevens, the head of NHS England, says medics and the NHS are learning new things about this virus all the time.
Sir Stevens said they are changing the way they work all the time to keep pace with emerging information.
He also said they are continuing to be vigilant so they are ahead of any second wave.
The problem is medics in Italy pointed to this phenomenon right at the start of this pandemic, and apparently Germany has been issuing oximeters for months.
So this isn't anything new and had the NHS cottoned on to this sooner many, many lives might well have been saved.
It would be churlish not to agree this is a huge step forward, but equally it would be remiss of me not to question why it's taken so long and ask how many lives could have been saved if the NHS had done this months ago.
Coronavirus: Everything you need to know: