This howto contains my work and the work of others from the Trixbox forums.  

Here are the steps for installing chan_mobile with Trixbox 2.3 Beta:
1. Let’s add a few components:

[trixbox1.local ~]# yum -y install bluez-utils bluez-libs bluez-libs-devel bluez-hcidump automake autoconf subversion gcc gcc-c++

2. Using the Package manager install the ncurses libraries, while you are at it you should also
install WebMin:

3. Type the following commands:

[trixbox1.local ~]# cd /usr/src
[trixbox1.local ~]# wget http://downloads.digium.com/pub/asterisk/old-releases/asterisk-1.4.13.tar.gz
[trixbox1.local ~]# tar xvfz asterisk-1.4.13.tar.gz
[trixbox1.local ~]# cd asterisk-1.4.13
[trixbox1.local ~]# ./configure
[trixbox1.local ~]# make

4. Type the following commands:

[trixbox1.local ~]# svn co http://svn.digium.com/svn/asterisk-addons/trunk asterisk-addons-trunk
[trixbox1.local ~]# cd asterisk-addons-trunk
[trixbox1.local ~]# svn update -r 421
[trixbox1.local ~]# cat chan_mobile.c | sed -e 's/ast_debug(1,/ast_log(LOG_DEBUG,/' | sed -e 's/, config_flags);/);/' > chan_mobile_1.4.c
[trixbox1.local ~]# mv chan_mobile_1.4.c chan_mobile.c
[trixbox1.local ~]# ./configure --with-asterisk=/usr/src/asterisk-1.4.13
[trixbox1.local ~]# make clean
[trixbox1.local ~]# make menuselect

Press 1, Select chan_mobile (deselect other stuff) and then Type “x” to exit the menu

NOTE: I just left the default selections... and hit an "x" without deselecting items...

[trixbox1.local ~]# make
[trixbox1.local ~]# make install
[trixbox1.local ~]# cp /usr/src/asterisk-addons-trunk/chan_mobile.so /usr/lib/asterisk/modules
5. Load chan_mobile.so
(asterisk -r (and then...) module load chan_mobile.so)
6. cp /usr/src/asterisk-addons-trunk/configs/mobile.conf.sample /etc/asterisk/mobile.conf
7. nano /etc/bluetooth/hcid.conf and replace the contents with:

options {
autoinit yes;
security auto;
pairing multi;
passkey "1234";
}# Default settings for HCI devices
device {
name "Asterisk PBX";
class 0x000100;
iscan enable; pscan enable;
lm accept;
lp rswitch,hold,sniff,park;
}

8. /etc/init.d/bluetooth restart

You'll probably be told that your system couldn't stop bluetooth (because it wasn't running) and
then it'll restart.