Who has the best geoIP and phone number checking software
 

I have been working on a project where a user submits a form and we collect the lead to call him back and help complete the sale. I am looking for the best geo IP software out there so that I can display the correct information for ads, as well as provide a local number for the customer to call.
Also, does anyone know of any software that will check to make sure the phone number the customer submits is valid, or at least valid number of digits/correct area code?

I think maxmind geocity is best.

You'll need a little custom work with maxmind's db.

Not very difficult for any coder.

+1 for maxmind

Thank you guys for your input.
Any other suggestions? We have not had the best luck with maxmind. Also, any ideas about the phone number checker?

www.geoplugin.com

broked's service, is more accurate than maxmind