You can find some serial lcds out there. Some of them are pure serial, in that it processes text normally, and handles newlines, carriage returns, etc. just like the serial monitor does. One is Liudr's serial lcd backpack. He has several different modules, so go over to the store to see the options: http://www.inmojo.com/store/liudr-arduino-and-physics-gadgets/item/serial-lcd-back-pack---phi-panel/
Of course, you could go really old school, and find a working VT-100 and make/buy a DB-9 cable, but if you don't have space for a laptop, you probably don't have space for a real serial monitor.
Many of the Digi-ole LCDs/OLEDs/TFTs support either a serial port, i2c, or spi, depending on how you set a jumper in the back. By default, it comes up in serial mode at 9600 baud. Note, you will need to run the digi-ole library, as you have to program it as a graphics lcd (the library gives you the standard print interface however). I have the 2.7" 128x64 LCD version, and have used it occasionally: http://stores.ebay.com/Digole-Digital-Solution?_trksid=p2047675.l2563
. If you already have a display, it looks like digi-ole has just the bare board that works with various displays: http://www.ebay.com/itm/Universal-Serial-UART-IIC-I2C-SPI-128x64-LCD-Adapter-Arduino-Lib-7-Fonts-Graphic-/370837649608?pt=LH_DefaultDomain_0&hash=item5657a578c8
You could of course switch to using i2c or spi, and then you have many more LCDs/OLEDs/TFTs to choose from.
Another solution I've used at times, is hook up a bluetooth HC-05 transceiver to the microprocessor, and then use apps on my Android cell phone as a serial monitor. If you are using some selected flavors of Arduino and have an Android phone with USB OTG support, you can use the ArduinoCommander app to mimic the serial port normally used by USB.
You can even run the IDE and download sketches with ArduinoDroid. I don't have a tablet with USB OTG, and I tend to think running it on a normal phone would be painful with the screen real estate, so I haven't tried it.