Database constraints: maintained plugins?

Are there any plugins that - add support for foreign key constraints - create corresponding validations for NOT NULL constraints etc. - are still maintained

In the past, I've used several plugins by RedHill Consulting, but apparently the company does no longer exist and the plugins are not maintained anymore. Looking around on

http://agilewebdevelopment.com/plugins

the state of similar plugins appears to be equally iffy. Are there any suggestions for alternatives?

Michael