Hardware-based Serial Port Monitor

I experience some strange behavior of a device. A software based serial port monitor does not show anything unusual. There might be some cross-talk or related issue. For that I woould like to use a HW- base serial port monitor that I can use on the device side. The requirements are:

1) MUST work with a laptop (for FAEs (Field Application Engineers) 2) Support for up to 38400 bps (higher is better) 3) Items should be time stamped so that event can later on be correlated with the serial port events. 4) Real-time monitoring is prefered, i.e. not something that has to be downloaded afterwards

Any recommendations on monitors that at least satisfy 1-3 are highly appreciated.

Thanks