Via Mi Band 3/4 we can unlock our windows easily. Just follow the steps and comment for any query and also to thank :p
First, open the Mi Fit app (Free, Android | iOS) and access the Mi Band settings via the ‘Profile’ page. Scroll down on the settings page and tap on ‘Lab’ to find the newly added ‘Unlock Mi NoteBook’ option. Simply toggle it on to enable the feature.