Warehouse Data Collection (WaDaCo) exits as an app that you can run for your warehouse processes, including purchase order receipts. If you’re on Apps 10 there’s a new Aurena Native app for it on Android (with the Windows and iOS versions being released next week with Upd9). 
What kind of users are these?
 

Thanks for your reply. We are currently using Apps 9. The users are Site Managers, who tend to be on a customers site where goods will be delivered. Rather than messaging the back office to receipt the goods it would be ideal if they Site Managers could do this themselves when they receive items on site.

WaDaCo exists on Apps9 as well, but only for Android and Windows (6.5 I believe). It might be something to explore - unless they have a laptop and could receipt from the client?

Mobile Work Order handles PO Receipts, but only receipts for specific work orders i.e. not stand alone and only for parts (not no-parts). 

If you have any plans to upgrade, in Apps 10 you could also run the process in your browser using Aurena and wouldn’t even need an app. 
 

Take a look at Cedar Bay….. 

Hi Harley, I sent you a message about our Novacura Flow PO receipt process that uses AI to analyze the parts being received in, automates the quality process if the wrong parts are identified and integrates with UPS (or any other logistics company) to automate the return shipping as well. 

Very robust and efficient solution that I would be more than happy to demo for you.  

Hi
In Notify Me you can add custom notification types with associated actions.

Best Regards
Tommy