I already answered on this post, but answering here too in case someone finds this one:
Junos Pulse (or Pulse Secure now) has an AppConnect SDK, this is straight from their guide:
The AppConnect SDK is a set of APIs and libraries, provided by Juniper, that allows mobile application developers
to directly open socket-based SSL VPN connections to a Connect Secure Gateway. From the point of view of the Connect Secure Gateway, these tunnels mirror all other forms of AppConnect tunnels. The integration is done at the code level. Any application that integrates with the AppConnect SDK needs to be recompiled and manually deployed to the end users. The AppConnect SDK is best leveraged by container solutions or in-house applications that are deployed without the use of an MDM solution. The APIs include authentication and connection management functions. Connections can be shared across multiple applications on a single device. Contact your Juniper sales representative for more details regarding AppConnect SDK.
Unfortunately as you can read in the last paragraph it is only available through your organisation Juniper sales representative.