Is there a way to enable the Spatial Extender in the Bluemix SQL Database or are there any plans to add this to the Service? I am aware that this functionality is available in the dashDB Service, however I would be interested to add geospatial queries to a standard application database that is not strongly focused on analytics and therefore the SQL Database Service seems to be a better fit.
If you are looking for a fully-managed service, then you may consider creating your tables as row based tables in dashDB (use ORGANIZED BY ROW in your create table DDL) so that it won't leverage the BLU features but will still have spatial extender.
Otherwise, as Henrik suggested, DB2 on Cloud is a good option if you like customization and don't mind the added responsibility of administrating and maintaining your database.