Requirement for a mesh network using Zigbee or similar technology

I have a requirement to design a proprietary monitoring system. (There’s some intellectual property involved so I’ll describe the system with a slightly altered purpose.) Imagine a large factory floor with dozens of devices scattered about (devices stay in one fixed location) and we want to be signaled when a device loses power. Every device has a free USB outlet. The concept is to design a dongle that plugs into each USB outlet, and simply draws the 5V, ignoring the data lines. The 5V powers a wireless chip like perhaps an XBEE device. Every device has an ID. The devices form an ad hoc network. A base station device then periodically interrogates the network (using e.g. a python api) to see if all the devices are there. If not, the missing devices are noted and an alert is generated.

The benefits I see are:

• No receivers have to be scattered around the facility since this is a mesh network.
• Low cost
• Propagation likely better than WiFi and this uses a simpler connect/disconnect protocol

My questions are:

• Is this possible with XBee or another widely available, inexpensive device?
• Are my assumptions correct?

I’d prefer to only get feedback from people that have real-world experience with mesh networks. I’ve already done a lot of research and know what is promised by various approaches, I’m now looking for real experience from people.

Thanks!