For OBD-II
ScanGauge-E
ScanGauge-2
Ultra Gauge
Turbo-Scan
Gamin OBD-II
Etc
are available
all of above mentioned are with display and with slightly different features and dimensions.
I found ultraGauge to be the cheapest and the best.
The reason for it to be cheap is not because its not good.
The main reason is
that
The manufacturer sells it their self. it is not sold on ebay etc. so that commission is not added to the cost that you pay.
well, I have just ordered one and it costed me 8500/- Pakistani Rupees
the base cost is 60$ if you apply the the mail in cash back reward(with in a month of buying), which I couldn't
the bracket/mount costed be around 9$
and shipping to my cousins place (with in U.S) costed me around 6$
so in total it costed me around 85$