Is there a way I can get the devices's serial number or MAC address?

MAC address depends on the interface so its not just one anyway you should be able to get both via a sh() command, i can add it on top of the IP in case, whats the usage scenario here? Devi serial number its not possible natively right now, its probably possible to fetch it via sh()

I'm calling an ASP, SQL webpage and want to pass a "unique" id, based on that I can feed back appropriate messages/statuses/results. I have written a file and stored a unique ID there but wanted to avoid having to create the extra file or the file being deleted. I have a team of 20 agents and wanted to install a widget and have messages/statuses posted to the appropriate agent. Having it with the IP would be good, I am not an sh() expert can you point me in the direction of how to get the serial number? Thank you for all your help!

I just checked and there is no way from the shell to get the device unique ID, this is due to the fact that Kustom has not permission to read that information. I will add a "mac" parameter to next version to allow you to extract that if you want, you can already get the device IP address using nc(ip) function

On my device, shell command "getprop ril.serialnumber" returns the device serial number

Could be a good candidate for an unique id