I use phone line surge protection all the time on alarm system phone connections.
Plain and simple.... they work.
Several companies make them but I use DiTek Surge protectors. They make them in UPS as well as stand alone for AC power, phone lines, data lines, and more. I don't install any systems that do not include at least one on the phone line. I use them on the SLC loops in fire alarm systems too and yeah... they work.
I had a few get fried ... one was literally burned by the strike, but after pulling it loose from the phone line, the alarm system dialer still worked perfectly. A direct strike will take out the suppressor and damage the gear but those kind of strikes are not too common.
They are made for data lines and cable as well as DSL so yeah, you can protect the router and switches in a data network with them.
http://www.ditekcorp.com/index.asp you can probably find them on Amazon and other direct to consumer alarm dealer websites. Where I purchase them is authorized dealers only.... and... many of them are not plug and play, they must be installed and grounded properly to function.