How accurate?

So I was wondering how accurate you think the results are from the equipment at the gym.
I know the heartrate estimate is way off, some times that thing will say I'm down in the 60's and I feel like i'm about to explode.  Maybe i'm in the 160's and it just cant register it accurately.
I'm not even sure about the heartrate monitor from my watch, because i have seen it much lower than I thought it would be.  That or my heart is doing some funky things.
I was working out a couple weeks ago and it said that my heart rate actually dropped for the first few minutes of my workout really low, down into the 40's and then it finally began to pick up and hit what I would consider normal for my workout.

How about the calorie expenditure?  Do you think they are accurate.  When I compare what I see online with what the machines say, they are never the same.  For example an hour on the elliptical machine and it reports it at 700 calories, 1 hour on the elliptical according to livestrong web site say 800 calories.  When I look at what my watch says (garmin forerunner305), I think the results are overly generous.

What if anything do you use to track your performance?

Thanks

Scott

I know the calorie expenditure isn't accurate because I'll run on the treadmill and my NikePlus will say one thing and the machine will say another. They also will disagree on how long I've worked out and how many miles I've gone.

Sometimes the heart rate monitors on our machines will go nuts and start taking random measurements even though I'm not holding the gripes. One set of machines (an older set) will start saying my heart rate is 96 no matter what I do. It's 96 when I'm walking, it's 96 when I'm running, it's 96 when I've just run for 20 min. It's infuriating!

So I just use them to get a general idea and to look for trends. I don't pay attention to the absolute numbers.

As far as calories, I have heard that it is about 70% of your body weight per mile.  I have no idea if its correct or not but it makes sence.  Lets say that 2 miles is the magic #.  If you do it in 10 minutes, you worked harder but only worked for 10 minutes.  If it takes 30 minutes, you didn't get the heart rate as high but were out there for 3 times as long.  It also uses weight as a factor.  The 130 lb 22 year old that just ran the 5 minute miles will burn fewer calories than a 200 lb person who did the same.  Again - 70% of your body weight per mile.

I have no clue if this is correct or not but it sounds logical to me.

Okay, so is it per hour or per mile? You said both. I don't think it can be per hour because that means I'm burning 77 calories during my 45 min. workout.

Im sorry.  It per mile.