The ultimate dream (IMO) is to use CHICKEN Scheme for everything. You can use it on the web [1], transpile to JS [2], run on Android [3], and since it's so portable, you can basically use it anywhere C code can run (embedded, etc.).

In practice though, it's not so glorious. CHICKEN still lacks strong numerics libraries (think Numpy, APL), and SPOCK, while useful, isn't as rugged or battle-tested as say, Clojurescript. It doesn't transpile to the greatest JS code, and I don't believe it works with all browsers (docs seem to indicate it needs work [2]).

I think it could be reasonable to eventually get this level of support, but the Scheme community is already quite small and needs people to work on these sorts of things. Right now, I'd say it's unreasonable to write everything (JS and numerics are the big problem) in CHICKEN, but we're getting close.

[1] http://wiki.call-cc.org/chicken-projects/egg-index-4.html#we... [2] http://wiki.call-cc.org/eggref/4/spock [3] https://github.com/chicken-mobile/chicken-android-template