Can I create a portable ad-hoc network between an iPad and other wireless devices?

I have a iPad that uses a third-part app to connect to and read data from a wireless hard drive. This works great in my house over my local network. What I want to do is create an ad-hoc network to use in my car or other remote site to basically just allow the wireless connection between the two devices, with no internet connection. I have used an ad-hoc network in the past to sync data between my iPad and my iMac, so theoretically it should be possible, but I can't seem to find out how to do it using the iPad to create the network. Is there a support article discussing this? Has anyone out there tried doing this? Any help would be appreciated.