The ELM-327 based OBD2 scan tools           

I will not ever use an ELM clone, off feebay.  (I have one, but only to evaluate it, it later blew up.) Made in China.
They are counterfeits fakes of the real ELM chip and they use  old buggy and stolen software, (and many come with a virus infected CD of stolen software.

I use exclusively for non hand held scanning, the products of  SCANTOOL.NET .
I have all 3 devices , the USB, bluetooth and wifi versions.
All 3 work perfectly with my $100 Palmer software.  (it can log anything for later viewing, see that in next link)

For hand held ?, I use above scan tool devices, and android phone APP, or better my INNOVA 3160 tool.

See me do full scans,  here. ( more than one tool used)

Next is the REAL chip, made by ELM.
The real ELM chip maker, is a company in Canada the programs the PIC processor with custom code that allows OBD2 communications in an easy way. 
The tools sold are 2 kinds, using a fake chip or real.
The fake tools all have a cheap and badly designed power regulator that has no life expectancy in any car. The 7805 REG. has no way to handle power surging. that is normal in all cars.
Top branded real tools avoid these pitfalls.
Why rip off ELM? (there  chip is only $20 that is the price of the software inside and the processor itself)
In China the cost is $1 + the cost of stolen software,at $0
Pretty hard to beat stolen pricing,,,, ?
That is also why the Scantool product costs more,  because the the power regulator and non counterfeit chips and  vastly better bundled non stolen software...
In the end, you do get what you pay for.

Here is a the EPA list of cars  that  fail readiness !, test and were announced, exempt.  Page 28 and 29.  21 cars, total.

I will only recommend this hardware version , it wireless and has better range. (however, the  USB version is the most easy to setup)


The best tool for blue tooth is here.  The bees-knees,   adhoc WIFI tool , designed In Phoenix Arizona, not in China, 100% legit.  I run their Mazda extended software too.  Mazda factory scans. "live data stream"

Click the below link to my dedicated WIFI page.

My WIFI install report, here.

Parting Shot:
You do get what you pay for,  and for $7  a free virus on every CD and/or very relic stolen software that is dumb as a brick.

The above is 100% opinion 
rev 6  ++++  6-1-2013 ,, 7-4-2015 cut out all the old stuff.