These are physical hardware keyloggers that are completely transparent from computer operation, and no software or drivers are required. International keyboard layouts are also supported.
See the comparison chart as some versions have a clock/battery for times-stamping keystrokes. Some have a module for sending keystrokes via wireless so you don’t need full physical access again and can obtain keystrokes immediately via TCP direct stream or have keystrokes sent to you via email.
|PS/2||USB Pico||USB WiFi Premium|
|Keyboard Connection Type||PS/2||USB||USB|
|Date and Timestamp||No||No||Yes|
|Wireless LAN Module||No||No||Yes|
|USB Mass Storage Mode||Yes||Yes||Yes|