This is a new feature that Microsoft has announced for US, UK and Canada Business Premium customers. It basically helps to track your miles on the road that you have used for customer visit, partner meetings or trade conference by using your on car. This data also can be used tax deduction or expense reimbursement.
MileIQ offers smarter way to track your miles with automatic drive detection and mileage logging, easy one-swipe classificatio0n as business or personal, and comprehensive reporting.
Reporting is also very strong and it is available only for you unless you wish to share it with your company.
If you are not sure whether your office 365 subscription covers MileIQ, you can create/sign in in to MileIQ and when prompted, enter your work email so Microsoft can check your eligibility.