I think that there is no restriction, but you'll have to publish this as a "non-deployable" and "paid via vendor" because you'll have an iphone app and not UPM installable add-on.
Here's an example of simular add-on https://marketplace.atlassian.com/plugins/com.obss.plugin.jiraclient
Go through the Marketplace docs for more information:
Here's some quotes:
What's the difference between deployable and non-deployable add-ons?
The Universal Plugin Manager (UPM) can install add-ons automatically into Atlassian applications. However, some items in the Atlassian Marketplace may not be suitable for automatic installation.
The Create new add-on form has a Deployable option that indicates whether an add-on installs with UPM. You should not check the Deployable option if your add-on consists of multiple JARs. The Atlassian Marketplace and UPM do not support Try, Buy, Install, Upgrade, and Renew buttons for non-deployable add-ons. Non-deployable add-ons cannot be sold under the Atlassian Marketplace Vendor Agreement as they do not support the UPM licensing API.
Additionally, if your add-on requires multiple downloads, configuration or license files on the file system, or if your add-on is not meant to be installed into the host product (like JIRA Client, for example), then do not check the Deployable option. Your add-on is still available for download, but the UPM does not attempt to install it in the host product.
Customers pay a fee to use your add-on. Customers purchase add-ons directly from you or your external website. You supply your own licensing and billing system.
The Jira Marketing team is putting together an ebook on migrating to Data Center. We're looking for pro tips on how you staffed your project team and organized your Proof of Concept. Share yo...
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG
You're one step closer to meeting fellow Atlassian users at your local meet up. Learn more about AUGs