On the simple and easy end of the spectrum, you can export out a .csv file (comma separate value) and import that into Quickbooks, among other accounting software solutions. Of course, that requires a manual process, which may not be a bad thing because it may be a part of your workflow.
You can automate this even more by using 3rd party apps and other software. One app that we've integrated with is Zapier, which allows you to go in and out of Allmoxy and in and out of lots of other web apps. So, if you use Quickbooks online, you can send data in and out of the two automatically. Of course, you need to set up Zapier, so here's a link to the invite: Zapier invitation
You can also use Transaction Pro.
There may be others as well, if you find them, please let us know so we can add them here!
As far as security, everything you're doing on your own network and between your own computers is just as secure as everything you're doing now, nothing changes. If you're sending data through Zapier, there is probably another layer of encryption, but I'd have to verify that.