When you hack your laFonera and disable the heartbeat/autoupdate function or install a new firmware, FON will notice that and maybe lock your account.
I wrote a little bash-script which simulate a laFonera. You can run this script on your normal PC and it checks once a day if there is a new firmware version. I guess this check is the heartbeat of the laFonera. Older versions of the FON Router also connect http://download.fon.com/heartbeat.php but so far I wasn't able to find out if laFonera connect this website, too.
To run the script you need two things. First the public key of the fon server. You can find it on every laFonera. Download it with:
scp email@example.com:/etc/dropbear/key .
Maybe you have to replace the IP of your laFonera. And, of course, you need ssh enabled on your laFonera.
Second you need the dropbear-ssh-client: dbclient In Debian the package is named dropbear. openssh seems not to work. Nobody knows why.
Download the script from my webpage http://futejia.fu.funpic.de/simthefon.sh (safe as)
Before you run the script the first time, you have to edit three variables.
FONKEY=/home/futejia/fon-hack/key #the path to the fon-public-key you downloaded before
WLMAC=00:18:84:**:**:** #the WLAN mac-adress
MAC=00:18:84:14:**:**:** #the WAN mac-adress
You can find out this mac adresses while running ifconfig on your laFonera. eth0 is the WLAN mac-adress and ath0 is the WAN mac-adress. You can also find the WLAN mac-adress on the backside of the laFonera case.
Now you are ready to run the script. Please report any errors and give feedback. I hope the script is helpfull.
And please: If anybody outhere knows if the laFonere do more heartbeats than downloading the firmware, please leave a comment.