You could implement hook_theme_registry_alter() and modify the status_message entry to process through your function.
[status_messages] => Array
(
[arguments] => Array
(
[display] =>
)

[type] => module
[theme path] => modules/system
[function] => theme_status_messages
[theme paths] => Array
(
[0] => modules/system
)

[preprocess functions] => Array
(
[0] => template_preprocess
)

)
You could alter the "theme paths" and "function". Devel Themer does something similar to run every entry in the theme_registry through it's own function.


-----
Adam A. Gregory
Drupal Developer & Consultant
Web: AdamAGregory.com
Twitter: twitter.com/adamgregory
Phone: 910.808.1717
Cell: 706.761.7375


On Thu, Jan 28, 2010 at 8:22 AM, James Benstead <james.benstead@gmail.com> wrote:
I'm working on this now. My approach is to override theme_status_messages(), so that I can change the status messages right before they're output. I know how to do this in a theme, but how do I do it in a module?

2010/1/25 Adam Gregory <arcaneadam@gmail.com>

Yep, totally agree. There are some issues open to create a hook_message_alter some of which seem to have some traction, but it will be D8 before this makes it in to core.

-----
Adam A. Gregory
Drupal Developer & Consultant
Web: AdamAGregory.com
Twitter: twitter.com/adamgregory
Phone: 910.808.1717
Cell: 706.761.7375


On Mon, Jan 25, 2010 at 3:10 PM, Michael Favia <michael.favia@gmail.com> wrote:
On Mon, Jan 25, 2010 at 2:07 PM, Adam Gregory <arcaneadam@gmail.com> wrote:
> template_preprocess_page and you can access and alter the message
> array/variable before it hits the theme.

Technically it has already hit the "theme" because you're editing the
preprocess function. But you are correct that hopefully this will work
for a single site implementation that needs this. However the need and
use for a hook at the module level is still apparent and valid. -mf