[CentOS] Check integrity or rootkits on remote server?

Hello,

when one has physical access to a computer, he can run something like tripwire, with keys and checksum on a separate, write-only media, to verify the integrity of the system.

What if the system is a remote one (in my case Centos 4.3 on a User Mode Linux VPS some hundred of KMs from here)?

Does it still make sense to run tripwire remotely? If yes, how, since you cannot plug a floppy or USB drive in the machine?

What if tripwire was never ran? Does it make sense, on a Centos system without physical access, to download there and run remotely one of those rootkit detection tools? Would its findings be surely accurate?

Generally speaking, how does one handle these issues on remote systems? Thanks in advance for any comment,

Marco