A portable LCD TV is no longer a luxury item reserved for those that have an excess of disposable income.  With the price of portable LCD TVs dropping below $100 in many cases, they have become a mass market product.  Just as owning portable music players have become a part our cultural experience, many are predicting the same for the digital portable TV.
Technically there is a difference between a handheld TV and a portable TV monitor.  The portable LCD TV monitor is similar to a computer monitor in that it will not display images unless it is connected to a source.  The monitor requires a separate TV tuner in order for it to function as a television.  So if you want a single unit function as a portable TV confirms that it has a tuner built in.  To take this a step further, many purchasers desire the option to play DVDs in addition to watching TV programming.  In this case,   a portable LCD TV DVD player (otherwise known as a portable LCD TV combo) is a better choice.

Depending on your anticipated use, you will want to pay attention to some of the following features:

Screen Size: There is a wide choice of screen sizes available.  LCD screen size can vary from # inches to as large as 16 inches.  Of course your choice will be dictated by the desired degree of portability, anticipated screen viewing distance and budget.  Sizes vary from 3 inches to about 16 inches, with most units falling within 7-10 inches.  Should you desire a larger portable TV and already own a laptop, you may want to consider a separate tuner and use your laptop screen.
Screen Aspect Ratio:  If your primary intent is to watch DVDs in the wide screen (16:9) format, then you will want to look for a portable LCD wide screen LCD TV.  Many will still prefer the standard aspect (4:3) screen ratio, particularly for television viewing.

Battery Type and Run Time: If one of the primary reasons for acquiring a digital portable TV is to have on hand in the event of power outages, then the battery run time should be a primary consideration.  In addition in some of the less expensive units, the batteries are permanently built into the internal structure of the TV.  In this case when the battery wears out or mal-functions, you are left with a useless TV.  A much better option is to look for a portable TV that has a removable battery.  Not only can you easily replace it should it go bad, you have the option of purchasing an extra battery for backup and extended usage.   Many portable TVs have adapters that enable the screen to be powered by Ac and Dc (think car use) as well as battery.

  You would think that this would be a standard feature in any handheld device, but there are actually some potable TVs that do not offer this.  If you would like the flexibility to use your portable LCD TV for games look for a full compliment of A/V inputs.

Whether you are looking for a portable LCD TV for emergency use, recreational use such as camping, or mobile unit to watch your favorite sports event on the go, there are many quality handheld TV models available.  Just make sure that you investigate the choices thoroughly to insure you that the TV you purchase will meet all your needs.