I tried out a little gizmo for my Canon T2i, priced b/w $20-40 (Canon's is $150), that I bought on the Internet. It's an intervalometer, or a "remote switch with digital timer" that plugs in at the side of the dslr:

Aputure brand intervalometer on Amazon (mine is a Shutterboss from B&H)

Here's what it does:

Time lapse, the Grottos outside of Aspen

Although it should be apparent (wasn't at first to me), an intervalometer doesn't shoot video, but a series of images that you later combine in a post-production program like Windows Live Movie Maker to create a "clip."

On a hike or bp, this is a great way to capture time-lapse clips of sunsets, clouds against mountains, a flower blooming, etc.

Upside:
These things are light. It only adds under 5 oz. to your pack (with the two AAA batteries included), although you'll definitely need to carry a light-weight tripod for the thing, so there is more weight.

Downside:
There are several negatives to overcome. First, you'll definitely slow your hiking party down. It takes a minute to set up, then you're taking five-minutes worth of shots for a 10-second clip. They just might leave you behind.

Second, these cheapy intervalometers are missing an important "on-off" button. So you have to take one of the batteries out to save them when not in use.

I'm still trying to figure out how to lock the mirror up during the shooting sequence (it's done in a custom menu.) Because shooting a sequence of 100 images is a lot of mirror-banging.

There is another way to take time lapse to insert in a video and that is to shoot the scene with the camera on a tripod, and then in the post-production program, like Windows Live Movie Maker, you just double the speed of the clip. I used this on the clouds-and twin-peaks clip in the following video -- it's at double the normal speed.

I love being able to do video (and time lapse) along with high-res stills with the lightweight Canon T2i, but have lots to learn to get it perfected. Here's a 5-minute video of a trip last week to Aspen that included a hike (more of a "posthole") to Crater Lake since we ignorantly left the snowshoes back home in Denver:

Aspen, early June, 2011.

BTW, the intervalometer has several functions (two, interval and continuous-shot are used for time lapse.) It can also be used for extra-long exposures at night or for stars in the sky, the Northern Lights and more.