This plugin adds a 'sendgrid' command to Heroku's CLI client, making it possible (and easy) to view your email usage during the current month.
Luckily, Heroku's client makes it very easy to install plugins:
heroku plugins:install git://github.com/hone/heroku-sendgrid-stats.git
For the current month:
$ heroku sendgrid
+----------------------------------------------------------------+
|    date    | requests | bounces | clicks | opens | spamreports |
+----------------------------------------------------------------+
| 2010-12-01 |    12342 |      12 |  10223 |  9992 |           5 |
| 2010-12-02 |    32342 |      10 |  14323 | 10995 |           7 |
| 2010-12-03 |    52342 |      11 |  19223 | 12992 |           2 |
| Totals     |    97026 |      33 |  43769 | 33979 |          14 |
+----------------------------------------------------------------+
The command also accepts the optional parameters year= and month=. For example:
$ heroku sendgrid month=6
+---------------------------------------------------------------+
|    date   | requests | bounces | clicks | opens | spamreports |
+---------------------------------------------------------------+
| 2010-6-01 |        0 |       0 |      0 |     0 |           0 |
| 2010-6-02 |        0 |       0 |      0 |     0 |           0 |
...
| Totals    |        0 |       0 |      0 |     0 |           0 |
+---------------------------------------------------------------+
$ heroku sendgrid year=1970 month=1
+---------------------------------------------------------------+
|    date   | requests | bounces | clicks | opens | spamreports |
+---------------------------------------------------------------+
| 1970-1-01 |        0 |       0 |      0 |     0 |           0 |
| 1970-1-02 |        0 |       0 |      0 |     0 |           0 |
...
+---------------------------------------------------------------+
Please see MIT-LICENSE for more details
Copyright (c) 2010 Terence Lee.
Thanks to Daniel Lamando