The diagnostic reports are in the section:
General >> About >> Diagnostics & Usage >> Diagnostics & Usage Data
I wrote a Python script that extracts info from the LowMemory reports. It prints out the names of the processes and the amount (in MB) of memory that each was using.
Here's the script: processLowMemReport.py
(It is published under the MIT licence.)
Sample output (from my iPhone 3GS):
| 1PasswordPro | 7.230 |
| AppleIDAuthAgent | 0.996 |
| BTServer | 1.023 |
| CommCenterClassi | 2.082 |
| Medieval_iphone_ | 36.859 |
| MobileMail | 11.609 |
| MobilePhone | 4.941 |
| Music~iphone | 10.059 |
| Pastebot | 4.453 |
| Preferences | 3.215 |
| SCHelper | 0.633 |
| SpringBoard | 29.078 |
| Tweetbot | 7.816 |
| UserEventAgent | 1.664 |
| absinthed.N88 | 0.531 |
| accountsd | 1.043 |
| aggregated | 1.137 |
| aosnotifyd | 1.918 |
| apsd | 0.965 |
| awdd | 0.762 |
| configd | 1.531 |
| dataaccessd | 10.750 |
| fairplayd.N88 | 0.633 |
| fseventsd | 1.141 |
| geod | 1.285 |
| iapd | 1.254 |
| imagent | 1.992 |
| installd | 4.457 |
| launchd | 0.480 |
| locationd | 3.000 |
| lockdownd | 1.312 |
| mDNSResponder | 0.754 |
| mediaremoted | 0.801 |
| mediaserverd | 4.160 |
| misd | 0.168 |
| networkd | 0.582 |
| notifyd | 0.898 |
| powerd | 0.543 |
| scrabble | 15.738 |
| securityd | 0.848 |
| syslogd | 0.445 |
| ubd | 1.273 |
| wifid | 1.117 |
| yap.TV | 3.730 |
