Editing by multiple users
Opening and editing the same file (on a sharepoint/OD4B site) in Excel app by multiple users, like it is possible in Excel online.

= 2016-12-05 =
Great news. If you have build 16.0.7426.1015 or later, you have the ability to co-author with others on files that are stored in O365 or OneDrive.com (you can both edit at the same time and not lock each other out of the workbook)
Enjoy!
Dan [MS]
2016-05-13 – Good news, we’ve started work on enabling co-authoring in Excel for Android.
Cheers,
Dan [MS]