Checkpoint has a VPN-1 client for Linux, but it's only for Red Hat 7.2, and also not so good.
You should try Openswan (
http://openswan.org). It works very well, if you can configure a site-to-site VPN on your Checkpoint firewall. There's a good document about it at
http://home.zhwin.ch/~sna/PA/PAK2_2002_Sna01_A.pdf.
About Checkpoint SecuRemote, I'm still looking for a compatible solution for Linux. I haven't found a way to create a client-to-site connection between a Linux client, and a Checkpoint VPN-1 gateway. I'm also couldn't find a way to use Openswan in a client with no fixed IP address, because the site-to-site VPN connection demands a pre-configuration of the external gateways at the Checkpoint firewall.
Does anybody know how to do it?