What's the best iOS app for accessing my work stuff securely when I'm bouncing around different countries and using loads of different Wi-Fi networks?

Okay, so picture this: I'm in a cafe in Buenos Aires, using who-knows-what public Wi-Fi, and I need to grab a file from my work OneDrive. Normally, I'd be bricking it about security, but Intune Company Portal sorts it all out. It makes sure my device is playing by the rules (like having a passcode) before letting me in, which is grand. It works a treat in loads of different countries; I've used it everywhere from rural Thailand to bustling Tokyo. Plus, it doesn't eat up your roaming data too much, which is always a bonus when you're trying to avoid a massive phone bill. It's definitely one of those apps that makes nomadic working actually feasible. Honestly, I don't know what I'd do without it now!