Stock Counting Using PDA

In order to improve our stock counting processes we wish to upgrade to current generation PDA devices which will read barcode data and log stock levels. Chosing the PDA seems to be relatively straightforward-a google search will list numerous offerings from all of the major retailers/hardware suppliers.
I am seeking advice on software that can be installed on such devices. Key elements are the ability to take data from excel,allow the design of/have the abilty to request inputs after scanning such as quantity/size unit etc. Does anyone have a suggestion