I don't believe so, where the USB port from what i am aware of is disabled.
I am guessing you want to hide the box out of sight, where if you own a mobile or tablet device you could download the free Roku remote controller App from the device App Store which controls the NowTV box over WiFI.
If you own the NowTV smart box you will also need to use a WOL App on your device to initially switch on the smart box from hibernation mode, where the std white or black nowtv box doesn't need the WOL function to start the box up.
Just a thought, if Schnapps is right when he said, "I am guessing you want to hide the box out of sight", I just hope that you are not planning to put your Now TV Combo or box in a cupboard because these devices, like all electrical equipment, require air circulation to work properly.
Unfortunately, it's something that people tend to forget.
@xl5 Having had a quick play, the USB port on the Smart Box does provide enough power to charge an iPod so you should be fine to power an IR extender. But it doesn't provide power once it's in standby, so using a USB port on your TV would be preferable, otherwise you'd need to point the remote directly at the box to wake up initially.
@xl5 I'm not sure what gadget you had in mind when you refer to an IR extender.
I'm assuming by IR extender you are referring to the gadgets that have an IR receiver at one end to pick up IR signals from a remote which are then retransmitted by an IR transmitter at the other end and have a USB cable for power. On such gadgets the USB cable can be plugged into anything that will provide power to the unit - those gadgets don't control other devices through the USB connection but merely rebroadcast IR signals via the IR transmitter.
If you're thinking of something like the dedicated 'magic eye' senders with component connections that you used to get then those are specific to certain devices and wouldn't work with the NOW TV box (but I'm pretty sure they didn't use USB anyway).