In way over my head, and have only cobbled this together through copious copy/paste action.

Author: mikewest

config

@@ -0,0 +1,3 @@
+ngx_addon_name=ngx_http_static_etags_module
+HTTP_AUX_FILTER_MODULES="$HTTP_AUX_FILTER_MODULES ngx_http_static_etags_module"
+NGX_ADDON_SRCS="$NGX_ADDON_SRCS $ngx_addon_dir/ngx_http_static_etags_module.c"

ngx_http_static_etags_module.c

@@ -0,0 +1,67 @@
+/*
+ *  Copyright 2008 Mike West ( http://mikewest.org/ )
+ *
+ *  The following is released under the Creative Commons BSD license,
+ *  available for your perusal at `http://creativecommons.org/licenses/BSD/`
+ */
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_http.h>
+
+#define ALLOWED_METHODS (NGX_HTTP_GET|NGX_HTTP_HEAD)
+
+static void *
+ngx_http_static_etags_create_loc_conf(ngx_conf_t *cf);
+
+static char *
+ngx_http_static_etags_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child);
+
+static char *
+ngx_http_static_etags_post_handler(ngx_conf_t *cf, void *data, void *conf);
+
+typedef struct {
+    ngx_str_t path;
+    ngx_str_t type;
+} ngx_http_static_etags_loc_conf_t;
+
+static ngx_http_module_t  ngx_http_notice_module_ctx = {
+    NULL,                                   /* preconfiguration */
+    NULL,                                   /* postconfiguration */
+
+    NULL,                                   /* create main configuration */
+    NULL,                                   /* init main configuration */
+
+    NULL,                                   /* create server configuration */
+    NULL,                                   /* merge server configuration */
+
+    ngx_http_static_etags_create_loc_conf,  /* create location configuration */
+    ngx_http_static_etags_merge_loc_conf,   /* merge location configuration */
+};
+
+
+ngx_module_t  ngx_http_notice_module = {
+    NGX_MODULE_V1,
+    &ngx_http_static_etags_module_ctx,  /* module context */
+    ngx_http_static_etags_commands,     /* module directives */
+    NGX_HTTP_MODULE,                    /* module type */
+    NULL,                               /* init master */
+    NULL,                               /* init module */
+    NULL,                               /* init process */
+    NULL,                               /* init thread */
+    NULL,                               /* exit thread */
+    NULL,                               /* exit process */
+    NULL,                               /* exit master */
+    NGX_MODULE_V1_PADDING
+};
+
+
+static void *
+ngx_http_static_etags_create_loc_conf(ngx_conf_t *cf)
+{
+    ngx_http_static_etags_conf_t  *conf;
+
+    conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_static_etags_conf_t));
+    if (conf == NULL) return NGX_CONF_ERROR;
+
+    return conf;
+}