There will be times when you won't have access to the server runing your redis (heroku for example). And many of those services don't have an option to import data from file.
If you're using ruby you can copy data between two redis servers directly using redis commands DUMP and RESTORE.
Here's how I did it (it's not fast, it's actually pretty slow but it works):
redisSrc = Redis.connect :url => "redis://some.host.com:11111"
redisDest = Redis.connect :url => "redis://other.host.com:22222"
redisSrc.keys("*").each do |key|
data = redisSrc.dump key
redisDest.restore key, 0, data