Approach to load testing iOS app

I did a search on this but couldn't find a match, possibly due to several meanings of the phrase "load testing"... but what we are trying to do is to make sure our App (which is a medical device that MUST display updated data in a timely fashion) will process data at a required throughput, even if the iPhone gets busy -- e.g., if there are a bunch of apps open that require CPU attention.

The best test approach we can come up with is basically that... open a bunch of apps, and perhaps try to load the CPU by sending it a bunch of emails with large attachments.

But obviously that is just kind of a stab at the risk. Are there any better techniques out there, or tools? Thanks for any help.