Digi Embedded Yocto provides a mechanism to perform firmware update process from a local resource or remotely using Digi's Remote Manager. Both methods, once the new firmware package is in the final device, use the same mechanism based on a standard tool called SWUpdate.
A swupdate tool is a standard software created to update embedded products. Digi integrates this software into their update mechanism but doesn't modify the tool implementation. I see no problems with using a bare swupdate tool.