Just to clarify things, frying PC ports should not be an issue, due to ocervurrent protection implemented in most modern OS'es, be it any linux, windows,mac or whatever. Normal outcome would be N900 charging @ max 500 mA from USB port, or 1A from 2 ports using Y-cable. Worst case scenario should be temporaly disabling on-topic USB port by OS, shouting @ user that peripherial device exceed current limitation drain.

Of course all of this is unless there is some bug in overcurrent protection, that I'm not aware of (which got high chances to be the case), so use at Your own risk.

Thanks for great scripts, shadowjediknight!