heart rate calorie burn monitors - best - most affordable

I bought one from Target the other day (can't remember brand for $30).  I do have to put in my weight and I had some excercises programmed and you can at 1-3 activities.  I didn't like it.  I tried setting it up last night and it's just not for me.  I don't think it's accurate and it's very difficult to set up.

I do like the idea of a monitor for calorie burning more but heartrate monitoring is good too.  I know and like Polar, but they are expensive (for me at least).  I wonder if they can be or should be bought used? 

I'm not married to a particular brand, but want something good, easy to set up and affordable.

I found the monitor I purchased from Target.  Sportline Women's 910 Heart Rate Watch.  I am going to return it and want to find something better.

I have been using a Sigma PC-15 (approx £30) for the past 3 months which gives you readings in terms of time spent in different heartrate % zones and beeps when you move out of them, it's great for tailoring your workout ie...HIIT or just sustained cardio and also gives you a total for the number of calories burned off. 

It comes with a chest strap which is quite comfy under a sports bra and also displays readouts on most gym machines automatically too, but can affect the ones next to it so make sure you have an empty one either side of you or other people get puzzled!

However sometimes when the contact of the strap against the chest is lost (usually when sretching) it doesn't give a signal or readout but will pick up where it left off when it the contact is made again.

I got a bit fed up of having to continually look at it to see if it was working and recently splashed out on a Vivago Personal Wellness Manager (£100 on offer!) as it takes sensor readings directly from the wrist and does not have a chest strap/transmitter belt.  However, I am using it for the first time today so will have to see how I get on with it!

I also bought a similar watch from Target and found that it was difficult to set up.  When I did manage to set it up I dont think it was very accurate.  I havent bought a new one yet but did look on Amazon the other day and they had several new and used varieties to pick from.