Most phones/tablets actually expose a USB OTG port (cable detect switching from USB device to USB host), which most certainly can be used as a USB host so long as the kernel supports it and you use a USB OTG host cable.
http://developer.android.com/guide/topics/connectivity/usb/host.htmlUSB host mode is supported in Android 3.1 and higher
To fully enable OTG support, you need way more than just a phone (or tablet) with a newer OS. See
here.
You need a list of things, including 1) an OS higher than 3.1 (which means ICS or JB for any phone), 2) compatible hardware (not every phone uses an OTG port), 3) OTG drivers (which usually means a rooted kernel), and finally 4) device drivers (BFG and CGMiner use different drivers for FPGA and ASIC devices).
If you look at EasyMiner on the
Android Market, it specifies all 4 of those. It requires the Nexus 7, which takes care of #1 (Nexus 7 comes with 4.2.2, as of today) and #2 (it has a proper OTG port, not just a USB port). #3 is taken care of by a rooted and 3rd party kernel, and #4 is most likely the reason it uses BFG instead of CGMiner.
If you were able to find a phone that could be had for less than $50, that has an ICS or JB ROM with the hardware and kernel to enable OTG support, I'm sure you could prolly use EasyMiner and the included BFG to mine on it.
I've got an old Droid X I bought off fleabay for $50 with a bad ESN years ago. Makes a wonderful media player or angry-birds-machine for myself or the kids. It has an ICS rom on it, but the hardware doesn't support OTG, and there are no kernels outside of the stock one, so that phone won't work.
