Blue Tooth or WLAN connection with either a WLAN/Blue-tooth printer or a router with a printer port.
http://www.quickbooksenterprise.com/featur...Integration.php is a PDA enabled version of Quickbooks.
You would have to contact them and talk to them about the software, but its very doable.
Quickbooks Enterprise starts @ $3k.
Tell us a little bit more about your service based business, that info would help in recommending an app that suits your needs.
What type of laptop/printer do you have now?
www.newlifetrimrepair.com
My company, a one man operation,

is a service for car dealers, body shops, and detail centers in North Jersey. No retail work. Only doing it for thirty years but getting the hang of it. It doesn't require too much in the way of software. I don't do estimates with it, really only do invoicing, statements, track receivables, and input the checkbook at the end of the year for tax purposes.
I have a Zaurus handheld but never used it yet. I dread learning curves. With software, anyway.

Other curves not so much.
Oh, also....I am a cheap basige.