Companies want to know how many people are back in the office. They're using water coolers to find out.

• Bevi, a Boston startup, makes high-tech water coolers that collect usage data.
• Some investors and hedge funds are using this data to track America's return to office trends, Bloomberg reported.
• The tracking places Bevi in the middle of a debate between remote workers and their employers. 

As companies adjust to a world of remote and hybrid work schedules, an unusual tool is emerging to help businesses keep track of their workers — the water cooler.