HELP!!! I wanna lose weight!

[Ideal08]

Ok, y'all, here's what I need.

I need a Heart Rate Monitor. I want it in the form of a watch. Why? Because I need to split my time (walk 3 mins, run 5 mins). So I want to make sure I'm not working out of my safe zone (HR-wise), and I want an easy way to keep track of how long I'm running/walking. I just did a quick search online, and they are VERY expensive. Now, I just spent an obscene amount of money on my shoes (obscene to me), and I don't want to spend more on this HR monitor watch than I spent on the shoes! So I need y'all's help.

Do you have a HR monitor of any type? If so, what is it, what does it do, and how much did you pay for it? Where did you get it from? Would you buy one used? I've never bought anything like this, so I haven't even checked Ebay or Amazon, because there are some things I won't buy used, and this may be one of them. Since I've never used one, I'm skeptical to buy a used one, because I won't know if it's broken or not, y'know?

So, help me!!! Because me and the treadmill are not getting along. I'd rather run outside. I mean, the marathon is outside, so I need to do all my training outside. And for that to happen, I need a timer of sorts that can split my time. I'm willing to use two devices, if need be, if that will save me money (like, a HR monitor and a separate stop watch).