I use the Garmin ForeRunner 110 GPS watch. You can get 3 version, the Unisex, women's version and the one for men.
The first 2 come without a HR strap but the men's watch comes with it. That one costs about £115 ish (sometimes a touch less) and the other 2 are around £90. I bought the unisex one then found the HR straps on ebay for £15 so I bought one and saved myself some cash.
It's a great watch and when I went to the hospital recently for an ECG I put the strap on while they were checking me and it turned out the reading was exactly the same as the hospital equipment so they're completely accurate.
The Nike+ watch looks much better and performs well but is more expensive and the HR monitor for it costs around £40. Not worth the added expense in my opinion as both watches and monitors do the same job.
Don't forget that if you're going to use a phone GPS app to measure distances they're not as accurate as a watch. They do give you a general idea of how you've done of course and can be useful but if you're looking to check if you're times/distances are improving on a week-by-week basis then they won't be any good. A good link going in to detail:
http://runneracademy.com/running-app...nning-watches/
But if all you want is to check your HR then it would be fine.
Make sure you're aware of the correct heart rate zone to be in when you run. My resting HR is around 55 BPM but when I'm on the road it averages out at 160BPM - staying in the correct zone will play a big part in whatever goal you're doing the running for (weight loss, improving cardio, endurance etc).