I would glad if you can make addition for device with Mi band 4, because it is much easiar and compactible rather than foot pod. Mi band 4 is have variety of sensor need for running such as heart rate, pace, km and others.
The Mi Band’s sensors are for recording data internally and not for broadcasting to another device. There are some fitness watches that can broadcast heart rate but nothing for foot pod. Easier to get a cheap foot pod or one of those treadmill simulation apps for your phone.