It's been almost half a year since I bought powermeter for USB, so it's time to start some test for 5V devices and maybe later even separate category, as I wrote on my blog.
First tested device is Huawei 3131 - GSM modem described long time ago. I plugged it on USB port of my laptop, waited to be detected and when it "stabilized" on idle, it took between 0.02 and 0.04A. Very rarely the were readings with 0.14A, but it's safe bet to assume it uses between 0.1 and 0.2W when idle.
Then I made connection using wvdial - when connection was idle, reading was exactly the same as before. When connection was used (typical WWW browsing), device took 0.26A, sometimes increasing to 0.31A. Then I made speedtest. During download energy draw stayed the same, but it was as high as 0.41A when uploading.
Probably those values heavily depend on singal quality, but right now I can assume it uses 1.55W while used and 2.05W was maximum noticed value.