according to a google io video about getting to know how much memory you app takes , you can use procrank and read the USS value of it.
i've tried it out on emulators (no matter which version i use - from 2.3.x to 4.1) and it works well , but running on an actual device , it didn't work (tested on galaxy s3 with android 4.0.4) . it's as if the command doesn't exist .
how could it be ? is there an alternative to get this USS value?