Foam Mattress Underlay $39.99 - Target
Foam fingers massage while you sleep.
Also SB $29.99 (save $30) or DB $34.99 (save $35).
Helps to relieve pressure points while you sleep.
Peaks and hollows allow air to circulate around your body.
HealthGuard - Anti-bacterial, anti-microbial protection.
If you're not sure about the magnetic properties of the Aldi underlay then this might be an interesting alternative.