Clever Idea or total waste of time? I can't decide..

[GoldenSnitch]

I've just discovered these

My first reaction was "ooh, clever idea" but it was closely followed with "what's wrong with a CD marker pen?" (my current method for remembering how long a jar has been open for)

What do you think?

Waste of money.

What's wrong with looking/sniffing/checking for mould?

at checking for mould

i assume they're not reusable? If you scratch something off

I dont even use a cd marker pen
sniff it

Ah yes but things like Pesto naturally look a but mouldy so how would you tell?

Plus, I cook for a 3 year old and like to be sure and needed to be more anal about ensuring things were fresh while I was pregnant recently.