[root@localhost ~]# systemctl status wpa_supplicant.service
wpa_supplicant.service – WPA Supplicant daemon
Loaded: loaded (/usr/lib/systemd/system/wpa_supplicant.service; disabled)
Active: active (running) since Sat 2013-08-10 09:10:57 EEST; 1h 21min ago
Main PID: 669 (wpa_supplicant)
CGroup: name=systemd:/system/wpa_supplicant.service
└─669 /usr/sbin/wpa_supplicant -u -f /var/log/wpa_supplicant.log -c /etc/wpa_supplicant/wpa_supplicant.conf -u -f /var/log/wpa_supplicant.log -P /var/run/…

Aug 10 09:10:57 localhost.localdomain systemd[1]: Starting WPA Supplicant daemon…
Aug 10 09:10:57 localhost.localdomain systemd[1]: Started WPA Supplicant daemon.

[root@localhost ~]# journalctl -r -o verbose -u wpa_supplicant.service
— Logs begin at Tue 2013-07-23 21:17:11 EEST, end at Sat 2013-08-10 10:31:29 EEST. —
Sat 2013-08-10 09:10:57 EEST [s=56a4cd388ac848b58942c2ec5eecaed3;i=180a8;b=f5fdeb90cc8747e394c56fe4d259697e;m=764c43;t=4e391c131b78b;x=2c4e6811b9d9d9a0]
PRIORITY=6
_UID=0
_GID=0
_MACHINE_ID=fbb0c4896a9c0f680475c0a07edd2c5a
SYSLOG_IDENTIFIER=systemd
SYSLOG_FACILITY=3
CODE_FILE=src/core/job.c
CODE_LINE=730
CODE_FUNCTION=job_log_status_message
MESSAGE_ID=39f53479d3a045ac8e11786248231fbf
RESULT=done
_TRANSPORT=journal
_PID=1
_COMM=systemd
_EXE=/usr/lib/systemd/systemd
_SYSTEMD_CGROUP=/system
_HOSTNAME=localhost.localdomain
_CMDLINE=/usr/lib/systemd/systemd –switched-root –system –deserialize 24
_SELINUX_CONTEXT=system_u:system_r:init_t:s0
UNIT=wpa_supplicant.service
MESSAGE=Started WPA Supplicant daemon.
_BOOT_ID=f5fdeb90cc8747e394c56fe4d259697e
_SOURCE_REALTIME_TIMESTAMP=1376115057859348
Sat 2013-08-10 09:10:57 EEST [s=56a4cd388ac848b58942c2ec5eecaed3;i=1809d;b=f5fdeb90cc8747e394c56fe4d259697e;m=7623bd;t=4e391c1318f05;x=bc954907c863e2c1]
PRIORITY=6
_UID=0
_GID=0
_MACHINE_ID=fbb0c4896a9c0f680475c0a07edd2c5a
SYSLOG_IDENTIFIER=systemd
SYSLOG_FACILITY=3
_TRANSPORT=journal
_PID=1
_COMM=systemd
_EXE=/usr/lib/systemd/systemd
_SYSTEMD_CGROUP=/system
CODE_FILE=src/core/unit.c
CODE_LINE=1038
CODE_FUNCTION=unit_status_log_starting_stopping_reloading
MESSAGE_ID=7d4958e842da4a758f6c1cdc7b36dcc5
_HOSTNAME=localhost.localdomain
_CMDLINE=/usr/lib/systemd/systemd –switched-root –system –deserialize 24

After _SELINUX_CONTEXT sometimes you can found useful information (Message) about occurred problems with Selinux label problems.