DC Battery Simulator Thing?

... and you can get adjustable DC power supplies with various output power capabilities, such as the Tenmas Ken mentioned, at places like http://www.mcmelectronics.com and http://www.partsexpress.com

... and, depending on your specific intention, you can get more modest little DC power supplies -- fixed voltage (e.g., "12 volt" which typically translates to 13.8 VDC, for devices that want 'car battery' voltage) or variable voltage -- with fairly low power capabilities, that may be all that you need.

e.g.,

13.8 VDC fixed, at 10 amp : http://www.radioshack.com/pyramid-ps15kx-10a-power-supply-w-car-power-jack/55057672.html#q=DC+power+supplies&start=6

6 to 12 VDC variable, at 2.5 amp: http://www.radioshack.com/enercell-6-12vdc-2-5-amp-high-power-ac-adapter/2730318.html#.VLQIAyvF_UU

As a side-note, some "modern" digital devices can be pretty picky about being plugged into the proper AC adaptors -- generic DC power supplies may not be suitable, depending on the application.

EDIT:

a couple of other thoughts :-P

Here's a direct link to MCM's entry page for power supplies:
http://www.mcmelectronics.com/category/Power-Supplies/0000001251

... and the analogous page for PartsExpress (their offerings seem to be pretty limited these days):
http://www.parts-express.com/cat/power-supplies/1474

A really good, cost effective source for things like these power supplies can be a local antique radio or amateur radio ("ham") swapmeet or flea market. Most locales have one, or several, such shindigs a year. They are big fun for the appropriate kind of geek-nerd, and can net the prepared searcher great equipment at very reasonable prices :- )

The power supply will deliver power (i.e., current at a given voltage) as demanded by the device ("load"), up to the capability of the power supply unit. The power supply will (should!) have a fuse or circuit breaker to protect itself (and also possibly its "load") from overloading. To answer your question, generally speaking it's fine to have more power capability in a power supply than you need. The only - potential - drawback would be a device with a problem such as an internal short and no built in fuse. A power supply that could deliver high current might immolate the device under test, under conditions where just using batteries for a power sourcemight not!

Well -- in the case of your example -- it's probably easier to just throw in four AAA batteries :- )

Power supplies are usually used for things like servicing/bench testing automobile electronics or for "breadboarding" new circuit designs.

You can certainly do what you're suggesting with a P/S capable of delivering 6V and a couple of clip leads. The remote won't draw much current; the current delivery capability of AAA batteries is pretty limited.

BTW, I'm a big fan of clip leads ;- )

IMG_0340 by mhardy6647, on Flickr

ahh, I see your point -- yes, makes sense.

The photo is a Fostex T90A supertweeter atop one of my Altec 604E "Duplex" (coaxial) studio monitor loudspeakers. The tweeters were experimentally installed with a very high, first order crossover and a variable L-pad to match the output of the (VERY) sensitive tweeters with the output of the (very) sensitive Duplexes.

The experiment was a success -- but the tweeters are still wired in as they appear in the photo :-P (I am nothing if not profoundly lazy...)

IMG_0341 by mhardy6647, on Flickr

It's not pretty when I butcher wood; I had them built for me by a cabinetmaker friend in Massachusetts.