I am not a developer on this project, but I had a similar requirement. Somehow, even enabling auth didn't seem to work for me. So I just disabled auth and changed this line in bootstrap.js: (Line 6):

mongoose.connect(config.mongodb.connectionString || 'mongodb://' + config.mongodb.server + '/' + config.mongodb.database);

I guess we can make it a conditional: if(!config.mongodb.user)...

When I followed the installation instructions on http://redotheweb.com/uptime/ on my ubuntu 14.04 machine the app failed to start due to mongo auth problem (default uptime config and fresh install of mongodb from ubuntu repos). I guess I could have fixed mongo and the config of uptime but I went with your workaround of just removing the user and password from line 6 of bootstrap.js