That's actually happening. Commercially you can buy a 0.55T system such as the Siemens Free Max for around $500k.
There are also developments in ultra-low-field fMRI (<0.1T) which use permanent magnets, which are estimated to retail in the five figure range, however it's more for structural usage (can identify a tumour or stroke progression).
What you are saying sounds like being able to control your own heart rate if you see it on a monitor. Maybe combining low resolution fMRI with models trained on higher resolution data, could give you enough visibility that you could learn how to activate other areas of the brain that you wouldn't normally use for tasks.
There are also developments in ultra-low-field fMRI (<0.1T) which use permanent magnets, which are estimated to retail in the five figure range, however it's more for structural usage (can identify a tumour or stroke progression).
What you are saying sounds like being able to control your own heart rate if you see it on a monitor. Maybe combining low resolution fMRI with models trained on higher resolution data, could give you enough visibility that you could learn how to activate other areas of the brain that you wouldn't normally use for tasks.