I was actually looking into this as well and found this one.

http://www.skyrc.com/index.php?route...&product_id=43

It's just for what we want and at a reasonable price. I picked one up on eBay for $50. I just ordered it so I can't give you my thoughts on the device, but I think someone here actually wrote a mini review on it.

Found it:
http://www.rctech.net/forum/radio-el...eed-meter.html

Hope this helps!