http://ipcheck.sourceforge.net/

Create file /etc/network/if-up.d/dyndns:
#!/bin/bash
cd /path/where/you/keep/pythonscript
python ipcheck.py -i gprs0 username password domain.dyndns.org

chmod 755 /etc/network/if-up.d/dyndns

First time, run manually:
python ipcheck.py --makedat -i gprs0 username password domain.dyndns.org
So it created it's data file.

And now you have autoupdating dyndns on the phone.. happy SSHing