The bed of nails is a shakti mat, or acupressure mat or pillow that has loads of little plastic spikes or nails.
I find it helps for my stiff neck and back, but only if I take my top off and lie on it for 1 minute or more.
If I put it on the sofa with my top on, it does nothing.
I also use it on my lower back.
The mats are pretty cheap, so worth a go.
other things that helped my neck and back include:
Saunas and ice baths
PEA – anti inflammatory supplement
The chesty cough medicine Guaifenesin is also a surprisingly good muscle relaxant. I’ve ordered some capsules but they’ve not arrived yet.