The current fuel level for Epson printers can be discovered using the escputils. To install them on a Debian based system (e.g. Ubuntu) use the following command
sudo aptitude install escputil
To get the current ink level, type in the following command (assuming your printer is connected to the default usb port)
sudo escputil -i -r /dev/usblp0
Remark
I just moved this article from my prior web site and retested it – and it does not work at the moment using Ubuntu 11.10. Reason should be bug 902970.