I was going to purchase the Web CallBack module but I did not. Below is the reason why not and how you can improve the module so that it looks more appealing to me and potentially to many other clients.
What made me give up on CallBack Module
Unfortunately, it appears that in order to work, the webserver hosting the site will need to access certain files on the FreePBX box. This is a big showstopper I think, with all concerns we have about keeping our FreePBX firewalled/isolated, we think it is a bit too much to ask to have our PBX system accessible from our web servers. Also, keep in mind that quite often websites are hosted on third-party platforms and servers which can add complexity to it.
How I think it should work:
You (FreePBX Inc) host a server that handles the Callme Back Button. I add the button to my website and all the logic is handled by the FreePBX Inc server. The FreePBX Inc server will do some work to make sure the string supplied from the website user is sane / not something dangerous to pass on to a FreePBX box.
My PBX then have a push and/or pull API so that when there is a new Callme task, it will get/receive the information from the FreePBX Inc server and handle the task. The FreePBX Inc server will be hosted on a fixed-ip (one or a range of addresses) so that I can easily open the firewall rules just for the FreePBX server to do the communication with my PBX.
I also think this module should then be free and I would pay per valid call request.
I hope you will find this feedback valuable. Sorry if this was not the place to post this content, in which case I appreciate if you tell me where it would be more appropriate.