There is possible to specify "uniq" = "1" for simple checks, like ICMP Ping, FTP, HTTP and other.

For example, the following API query is accepted without errors:
{
"jsonrpc": "2.0",
"method": "drule.create",
"params": {
"name": "test",
"iprange": "10.2.158.0\/24",
"dchecks": [

{ "type": "12", "uniq": "1" }

],
"proxy_hostid": "1010",
"delay": "3600",
"status": "0"
},
"auth": "****",
"id": 1
}