I have a little meter called a "Kill - a - Watt". It's about the size of a pack of cigarettes. You plug it into the wall socket and then plug your electrical device into it. I don't know if it reads amps directly - I toggle mine between V (I'm amazed at how a normal house plug varies) and watts. I've measured my entire bus on a 15A 120V plugin, and I've used it for measuring individual appliances. Also, it will show you how much "parasitic" draw appliances (microwaves, TV's, stereo systems, etc.) use all the time even if they're not "on"; it also shows wattage being pulled by plug in battery chargers etc. It's pretty light-duty so I wouldn't try to measure more than about 1500 watts but it sure works well for what it does.
I also use the "Mate" control box readout for my Outback system to check on voltages (it's particularly good for house battery voltage which the Kill - a - Watt" won't measure). IMO, we need different types of checks for different systems and conditions, but the inverter readout and a "Kill - a - Watt" are a pretty good combo. (And I need one of the little devices that shows you if the supply socket is wired right, has a a good ground, neutral, etc. - I'll get one in the next couple of days.)
If you want to have a little control over parasitic draws you should check out this item.http://amzn.to/17WOnPZ
It is primarily designed for entertainment systems. It automatically shuts off various items based on the power status of 1 item. For example, if you have a tv, home theater system, dvd player, satellite box, and video game, you could have the tv be the monitored item, and if it is off, the power would be shut off to the other items as well.
Could be very useful to prevent those minute draws that can drain batteries.