Best way to detect memory usage etc. on mobile device for debugging?

Hi

What's the best way, when developing, to detect memory usage and such while the app is running on the device?

So you can test it and see if something is causing it to run wild. I'm making an iOS/Android device so I want to try it on both slow and fast phones and I have a script that "adds on" memory usage as the user continues. I would like to monitor this (either in app, or from the debugger) to see what happens.

Any ideas?

Thank you