How does the gizmo do with yard work?

I've been wearing my bodymedia fit fitness gizmo while working in the yard. On average, I spend 2-3 hours outside a day working on yard stuff. While I'm out there I have done such activities:

• Ripping up sod with a manual sod remover - 3 hours. It said I was moderately active for about one hour with about 12000 steps for the day.
• Weeding flower beds by hand - 3 hours. Gizmo said I was moderately active for about 15 minutes. With about 6000 steps for the day.
• Planting annuals with a hand spade - 3 hours. Gizmo said I was moderately active for about 15 minutes. WIth about 6000 steps for the day.
• Planting larger shrubs with shovel - 3 hours. Gizmo said I was moderately active for about 25 minutes with about 7000 steps for the day.
• Digging up soil and removing it for stone pathway - 2 hours.  Gizmo said I was moderately active for about 25 minutes with about 7000 steps for the day.
• Hauling stones, positioning and leveling with sand - 3 hours. Gizmo said I was moderately active for about 30 minutes with about 8000 steps for the day.
• Shoveling mulch, hauling mulch and distributing mulch by hand and rake - 3 hours. Gizmo said I was moderately active for about 15 minutes with about 7000 steps for the day.

Compare that to 45 minutes of step aerobics:

• 20 minutes of moderate exercise, 10 minutes of vigorous exercise and about 10000 steps for the day.

This are somewhat accurate and a bit hard to compare super accurately, but either gardening isn't as 'active' as it seems or the gizmo just doesn't pick it up. It kind of stinks when you spend 2-3 hours outside working and come in to see that you've only logged 15 minutes of being active! I can get that much moderate activity going grocery shopping!

This morning I was out mulching the yard. I had to break up the compacted mulch on the driveway, shovel and lift it into a wheel barrow, roll the wheelbarrow to the side yard, dump it out, then with a pronged rake and a bit by hand, distribute the mulch around the perennials. I did that today for about 90 minutes between 8:45 am to 10:15 am. When I came in, it was 90 degrees outside, 96 with heat index and I was drenched. I could almost ring out my jeans shorts, t-shirt, bra and underwear. My gizmo said I was moderately active for 32 minutes and that I took 4000 steps. I was working pretty fast this morning to try to get the side yard done before it got too hot, but to be that hot and sweaty and "ugh" feeling and to see I got 32 minutes out of it? Kind of disappointing - though it is more than I've seen for other days doing similar things for even more time outside. 

So, I don't know how much info I get from the gizmo. It's fun in a way, but how accurate? Hard to tell. I haven't been dropping weight, but I've also been eating more, so maybe it is pretty accurate.  I'll keep checking and see.