You need to create infrastructure (Access Point mode) wireless hot-spot rather Ad-hoc hot-spot. In linux(ubuntu) i used ap-hotspot and which works for me(i got connected WP8 and Android 4.4, dont know about iPhones).
For installation
sudo add-apt-repository ppa:nilarimogard/webupd8
sudo apt-get update
sudo apt-get install ap-hotspot
Then configure it as
sudo ap-hotspot configure
It will asks for interfaces, Access point name(which can be anything you want to see as wifi_hotspot name), password(which is your wifi_hotspot security key).
Now, if you able to configure successfully and dont get any kind of Unsupported wifi errors(if you get that simply means, your wifi_card doesnt support infrastrucutre Access point wifi_hotspot, so can do nothing on it), then procceed.
So just now start your hotspot as
sudo ap-hotspot start
If you want to stop then
sudo ap-hotspot stop
If you wanna see all available commands
sudo ap-hotspot
You don't see this hot-spot running in any indicator or something, i am still finding it how to determine status checking of it.
I am using is from last few weeks, and no bugs(no side-effects too) yet. I am using Gnome-Ubuntu 13.10 amd64 sharing eth0 to my WP8.
SOURCE : http://www.unixmen.com/create-infrastructure-wifi-access-point-connect-android-devices/SOURCE : http://www.webupd8.org/2013/06/how-to-set-up-wireless-hotspot-access.html
