I haven't tried any possible solutions. Building an inhouse monitor is a possibility, but I would pay for a service if it was only $25 pm. Particularly if it included the option of buying Sys Admin/DBA support, charged hourly as required, with the aim being the effective outsource of day to day monitoring and tech support of a site.
I really like your idea to buy sys admin/dba support as a topup when needed. I would love to hear what you think of New Relic. They do have a $24 a month option if you commit to a year. Also what are your thoughts on free solutions like monit or Nagios.