Pseudo-alphabet is properly descriptive; on the other hand, pseudo-abecedaria is less formally correct, but more analagous in a stylistic sense.

I use "con-script" (hyphenated to avoid terminological warfare :-) which is short for "constructed script". It sort of comes from the -generally accepted- "conlang" ("constructed language").

BTW, here's one I recently made a font for (not featured on the site though):
http://shwa.org/
In fact I've sort of become a go-to guy for weird shtuff...
http://typophile.com/node/76536
Must've started with this:
http://themicrofoundry.com/ss_trajic.html

hhp

I might say these sorts of fonts are more of a faux con-script as their main purpose is to look like an alien language, which works just as well if you mash your keyboard for nonsense.
While you can use them as a substitution cipher for English (or whatever language of the Latin alphabet is that of the writer and/or reader), which is technically an English con-script and allows readers to decode it, the intent is still to represent in its fictional framework a language which is not English and does not sound like English when spoken aloud.

You can see that the Blambot site categorizes them as symbol fonts. This might seem like throwing two categories together for convenience, but it's hard to say there's a clear line to be drawn: I've seen Wingdings used in comics to represent an unknown language.

faux con-script

Ah, good point. So I would go for a variant of what Nick said: pseudo-script.

hhp

...Need to figure out how to translate Charlie Brown's parents speak into a font...

Ryan—

Probably need to use stronger meds…

phaw phaw phaw phaw, phaw phaw phaw...